Eaton Vance High Yield Municipal Income Fund

Class W Shares - EWHYX

Prospectus Dated
June 1, 2023

The Securities and Exchange Commission (“SEC”) has not approved or disapproved these securities or determined if this Prospectus is truthful or complete.  Any representation to the contrary is a criminal offense.

This Prospectus contains important information about the Fund and the services available to shareholders. Please save it for reference.

Fund Summary

Investment Objective

Fees and Expenses of the Fund

(1)The investment adviser has agreed to reimburse the total amount of the advisory fees paid by Class W shares. This expense reimbursement will continue through May 31, 2024.  Any amendment to or termination of this reimbursement would require approval of the Board of Trustees.  

Example. This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.  The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods.  The Example also assumes that your investment has a 5% return each year, that the operating expenses remain the same and that any expense reimbursement arrangement remains in place for the contractual period.  Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” the portfolio).  A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account.  These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund's portfolio turnover rate was  53%  of the average value of its portfolio.

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Principal Investment Strategies

Principal Risks

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Performance

Calendar year-by-year total return (Class W)

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Management

Investment Adviser.  Boston Management and Research (“BMR”).

Portfolio Managers  

Cynthia J. Clemson, Vice President of BMR, has managed the Fund since September 2004.

William J. Delahunty, Jr., Vice President of BMR, has managed the Fund since October 2021.

Purchase and Sale of Fund Shares

Class W shares are available for purchase only at the direction of the investment adviser or one of its affiliates on behalf of investors that are eligible clients of the investment adviser or its affiliates that have entered into a separate investment management or advisory agreement pursuant to which such clients pay an investment management or advisory fee, including investment vehicles that are sponsored, managed, advised or sub-advised by the investment adviser or its affiliates (such investment adviser or affiliate, an “account adviser”). An account adviser must submit redemption orders to the applicable financial intermediary. Shares of the Fund may be held only by eligible investors and cannot be exchanged for any other share class. The Fund reserves the right to redeem shares of any investor if the investor ceases to be an eligible investor. There is no minimum initial purchase amount or minimum subsequent investment amount for Class W shares.

Tax Information

The Fund’s distributions are expected to primarily be exempt from regular federal income tax.  However, the Fund may also distribute taxable income to the extent that it invests in taxable municipal obligations or other obligations which generate taxable income.  Distributions of any net realized gains are expected to be taxable.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund’s shares through a broker-dealer or other financial intermediary (such as a bank) (collectively, “financial intermediaries”), the Fund, its principal underwriter and its affiliates may pay the financial intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

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Investment Objective & Principal Policies and Risks

The investment objective and principal investment policies and risks of the Fund are described in its Fund Summary.  Set forth below is additional information about such policies and risks, as well as information about other types of investments and practices in which the Fund may engage from time to time.  See also “Strategies and Risks” in the Statement of Additional Information (“SAI”).

Definitions.  As used herein, the following terms have the indicated meaning: “1940 Act” means the Investment Company Act of 1940, as amended; “1933 Act” means the Securities Act of 1933, as amended; “Code” means the Internal Revenue Code of 1986, as amended; “ERISA” means the Employee Retirement Income Security Act of 1974, as amended; and “investment adviser” means the Fund’s investment adviser but if the Fund is sub-advised, it refers to the sub-adviser(s) providing day-to-day management with respect to the investments or strategies discussed.

Municipal Obligations.  Municipal obligations include bonds, notes, floating-rate notes and commercial paper issued by a municipality, a group of municipalities or participants in qualified issues of municipal debt for a wide variety of both public and private purposes.  Revenue bonds are payable only from the revenues derived from a particular facility or class of facilities or, in some cases, from the proceeds of a special excise tax or other specific revenue source such as payments from the user of the facility being financed.  Municipal obligations also include municipal lease obligations and certificates of participations in municipal leases.  A municipal lease obligation is a bond that is secured by lease payments made by the party, typically a state or municipality, leasing the facilities (e.g., schools or office buildings) that were financed by the bond.  Such lease payments may be subject to annual appropriation or may be made only from revenues associated with the facility financed.  In other cases, the leasing state or municipality is obligated to appropriate funds from its general tax revenues to make lease payments as long as it utilizes the leased property.  A certificate of participation (also referred to as a “participation”) in a municipal lease is an instrument evidencing a pro rata share in a specific pledged revenue stream, usually lease payments by the issuer that are typically subject to annual appropriation.  The certificate generally entitles the holder to receive a share, or participation, in the payments from a particular project.

Certain municipal obligations may be purchased on a “when-issued” basis, which means that payment and delivery occur on a future settlement date. The price and yield of such securities are generally fixed on the date of commitment to purchase.

The Fund may invest in zero coupon bonds, which do not make cash interest payments during a portion or all of the life of the bond. Instead, such bonds are sold at a deep discount to face value, and the interest consists of the gradual appreciation in price as the bond approaches maturity.  Zero coupon bonds can be an attractive financing method for issuers with near-term cash-flow problems or seeking to preserve liquidity.  Principal only investments entitle the Fund to receive the stated value of such investment when held to maturity.

Certain municipal obligations are issued with interest rates that adjust periodically.  Such municipal floating-rate debt obligations are generally indexed to LIBOR, the Securities Industry and Financial Markets Association index, the Consumer Price Index or other indices. Municipal floating-rate debt obligations include, but are not limited to, municipal floating-rate notes, floating-rate notes issued by tender option bond trusts, auction rate preferred securities, synthetic floating-rate securities (e.g., a fixed-rate instrument that is subject to a swap agreement converting a fixed rate to a floating rate) and other municipal instruments with floating interest rates (such as variable rate demand preferred shares and variable rate term preferred shares).  

The interest on tax-exempt municipal obligations is (in the opinion of the issuer’s counsel) exempt from regular federal income and state or local taxes, as applicable. Income from certain types of municipal obligations generally may be subject to the federal alternative minimum tax (the “AMT”) for individuals.  Investors subject to AMT should consult their tax advisors.

Issuers of general obligation bonds include states, counties, cities, towns and regional districts.  The proceeds of these obligations are used to fund a wide range of public projects, including the construction or improvement of schools, highways and roads, water and sewer systems and a variety of other public purposes.  The basic security of general obligation bonds is the issuer’s pledge of its faith, credit, and taxing power for the payment of principal and interest.  The taxes that can be levied for the payment of debt service may be limited or unlimited as to rate and amount.  General obligation bonds issued by municipalities can be adversely affected by economic downturns and the resulting decline in tax revenues, pension funding risk, other post-employment benefit risk, budget imbalances, taxing ability risk, lack of political willpower and federal funding risk, among others.  Revenue bonds can be adversely affected by the negative economic viability of the facility or revenue source. Industrial development bonds are normally secured by the revenues from the project and not by state or local government tax payments. They are subject to a wide variety of risks, many of which relate to the nature of the specific project. Generally, industrial development bonds are sensitive to the risk of a slowdown in the economy.  Many municipal obligations provide the issuer the option to “call,” or redeem, its securities. As

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such, the effective maturity of a municipal obligation may be reduced as the result of such call provisions and, if an investment is called in a declining interest rate environment, the proceeds from the called bond may have to be reinvested at a lower interest rate.

The values of zero coupon bonds and principal only investments are subject to greater fluctuation in response to changes in market interest rates than municipal obligations that pay interest currently.  The Fund is required to distribute to shareholders income imputed to any zero coupon bonds or principal only investments even though such income may not be received by the Fund as distributable cash. Such distributions could reduce the Fund’s reserve position and require it to sell securities and incur a gain or loss at a time it may not otherwise want to in order to provide the cash necessary for these distributions.

Credit Risk.  Investments in debt instruments are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Fund could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Fund may be required to retain legal or similar counsel, which may increase the Fund’s operating expenses and adversely affect net asset value. See “Lower Rated Investments.” Municipal obligations may be insured as to principal and interest payments. If the claims-paying ability or other rating of the insurer is downgraded by a rating agency, the value of such obligations may be negatively affected. The Fund is also exposed to credit risk when it engages in certain types of derivatives transactions and when it engages in transactions that expose the Fund to counterparty risk. See “Derivatives.”

In evaluating the quality of a particular instrument, the investment adviser (or sub-adviser, if applicable) may take into consideration, among other things, a credit rating assigned by a credit rating agency, the issuer’s financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. Credit rating agencies are private services that provide ratings of the credit quality of certain investments. Credit ratings issued by rating agencies are based on a number of factors including, but not limited to, the issuer’s financial condition and the rating agency’s credit analysis, if applicable, at the time of rating. As such, the rating assigned to any particular security is not necessarily a reflection of the issuer’s current financial condition. The ratings assigned are not absolute standards of credit quality and do not evaluate market risks or necessarily reflect the issuer’s current financial condition or the volatility or liquidity of the security.

For purposes of determining compliance with the Fund’s credit quality restrictions, if any, the Fund’s investment adviser (or sub-adviser, if applicable) relies primarily on the ratings assigned by credit rating agencies but may, in the case of unrated instruments, perform its own credit and investment analysis to determine an instrument’s credit quality.  A credit rating may have a modifier (such as plus, minus or a numerical modifier) to denote its relative status within the rating. The presence of a modifier does not change the security credit rating (for example, BBB- and Baa3 are within the investment grade rating) for purposes of the Fund’s investment limitations.  If an instrument is rated differently by two or more rating agencies, the lowest rating will be used for any Fund rating restrictions.

Lower Rated Investments.  Investments in obligations rated below investment grade and comparable unrated securities (sometimes referred to as “junk”) generally entail greater economic, credit and liquidity risks than investment grade securities.  Lower rated investments have speculative characteristics because of the credit risk associated with their issuers.  Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments.  An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs.  Lower rated investments generally are subject to greater price volatility and illiquidity than higher rated investments. Lower rated investments are considered primarily speculative with respect to the issuer’s capacity to pay interest and repay principal.

Because of the greater number of investment considerations involved in investing in investments that receive lower ratings, investing in lower rated investments depends more on the investment adviser’s judgment and analytical abilities than may be the case for investing in investments with higher ratings.  While the investment adviser will attempt to reduce the risks of investing in lower rated or unrated securities through, among other things, active portfolio management, credit analysis and attention to current developments and trends in the economy and the financial markets, there can be no assurance that the investment adviser will be successful in doing so.

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Duration.   Duration measures the time-weighted expected cash flows of a fixed-income security, while maturity refers to the amount of time until a fixed-income security matures.  Duration differs from maturity in that it considers a security’s coupon payments in addition to the amount of time until the security matures.  As the value of a security changes over time, so will its duration.  Various techniques may be used to shorten or lengthen Fund duration.

Interest Rate Risk.  In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise.  Generally, securities with longer durations or maturities are more sensitive to changes in interest rates than securities with shorter durations or maturities, causing them to be more volatile.  Conversely, fixed-income securities with shorter durations or maturities will be less volatile but may provide lower returns than fixed-income securities with longer durations or maturities.  In a rising interest rate environment, the duration of income securities that have the ability to be prepaid or called by the issuer may be extended.  In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate. Because the Fund is managed toward an income objective, it may hold more longer duration or maturity obligations and thereby be more exposed to interest rate risk than municipal income funds that are managed with a greater emphasis on total return. Certain factors, such as the presence of call features, may cause a particular fixed-income security, or the Fund as a whole, to exhibit less sensitivity to changes in interest rates. Certain of the Fund’s investments may also be valued, in part, by reference to the relative relationship between interest rates on tax-exempt securities and taxable securities, respectively. When the market for tax-exempt securities underperforms (or outperforms) the market for taxable securities, the value of these investments may be negatively affected (or positively affected). Certain countries and regulatory bodies may use negative interest rates as a monetary policy tool to encourage economic growth during periods of deflation. In a negative interest rate environment, debt instruments may trade at negative yields, which means the purchaser of the instrument may receive at maturity less than the total amount invested.  Changes in governmental policy, including changes in central bank monetary policy, could cause interest rates to rise rapidly, or cause investors to expect a rapid rise in interest rates. This could lead to heightened levels of interest rate, volatility and liquidity risks for the fixed income markets generally and could have a substantial and immediate effect on the values of the Fund's investments.

LIBOR.  The London Interbank Offered Rate or LIBOR is the average offered rate for various maturities of short-term loans between major international banks who are members of the British Bankers Association.  It historically has been used throughout global banking and financial industries to determine interest rates for a variety of financial instruments (such as debt instruments and derivatives) and borrowing arrangements.  In July 2017, the Financial Conduct Authority (the “FCA”), the United Kingdom financial regulatory body, announced a desire to phase out the use of LIBOR. The ICE Benchmark Administration Limited, the administrator of LIBOR, ceased publishing certain LIBOR settings on December 31, 2021, and is expected to cease publishing the remaining LIBOR settings on June 30, 2023. In addition, global regulators have announced that, with limited exceptions, no new LIBOR-based contracts should be entered into after 2021. Many market participants are in the process of transitioning to the use of alternative reference or benchmark rates.

Although the transition process away from LIBOR has become increasingly well-defined, the impact on certain debt securities, derivatives and other financial instruments that utilize LIBOR remains uncertain.  The transition process may involve, among other things, increased volatility or illiquidity in markets for instruments that continue to rely on LIBOR. The transition may also result in a change in (i) the value of certain instruments held by the Fund, (ii) the cost of temporary borrowing for the Fund, or (iii) the effectiveness of related Fund transactions such as hedges, as applicable.

Various financial industry groups have been planning for the transition away from LIBOR, but there are obstacles to converting certain longer term securities and transactions to a new benchmark. In June 2017, the Alternative Reference Rates Committee, a group of large U.S. banks working with the Federal Reserve, announced its selection of a new Secured Overnight Financing Rate (“SOFR”), which is intended to be a broad measure of secured overnight U.S. Treasury repo rates, as an appropriate replacement for LIBOR. Bank working groups and regulators in other countries have suggested other alternatives for their markets, including the Sterling Overnight Interbank Average Rate (“SONIA”) in England. Both SOFR and SONIA, as well as certain other proposed replacement rates, are materially different from LIBOR, and changes in the applicable spread for financial instruments transitioning away from LIBOR need to be made to accommodate the differences. Liquid markets for newly-issued instruments that use an alternative reference rate are still developing. Consequently, there may be challenges for the Fund to enter into hedging transactions against instruments tied to alternative reference rates until a market for such hedging transactions develops.

Additionally, while many existing LIBOR-based instruments have contemplated a scenario where LIBOR is no longer available by providing for an alternative or “fallback” rate-setting methodology, there may be significant uncertainty regarding the effectiveness of any such alternative methodologies to replicate LIBOR. Not all existing LIBOR-based instruments have such fallback provisions. While it is expected that market participants will amend legacy financial instruments referencing LIBOR to include fallback provisions to alternative reference rates, there remains uncertainty

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regarding the willingness and ability of parties to add or amend such fallback provisions in legacy instruments maturing after the end of 2021, particularly with respect to legacy cash products.  Federal legislation has been enacted in the U.S. to assist with the transition away from LIBOR to new reference rates for instruments known as “tough legacy” contracts.  Although there are ongoing efforts among global government entities and other organizations to address transition-related uncertainties, the ultimate effectiveness of such efforts is not yet known.

Any effects of the transition away from LIBOR and the adoption of alternative reference rates, as well as other unforeseen effects, could result in losses to the Fund, and such effects may occur prior to the discontinuation of the remaining LIBOR settings in 2023. Furthermore, the risks associated with the discontinuation of LIBOR and transition to replacement rates may be exacerbated if an orderly transition to an alternative reference rate is not completed in a timely manner.

Derivatives. Generally, derivatives can be characterized as financial instruments whose performance is derived at least in part from the performance of an underlying reference instrument.  Derivative instruments may be acquired in the United States or abroad consistent with the Fund’s investment strategy and may include the various types of exchange-traded and over-the-counter (“OTC”) instruments described herein and other instruments with substantially similar characteristics and risks.  Fund obligations created pursuant to derivative instruments may give rise to leverage, which may subject the Fund to heightened risk of loss.  The Fund may invest in a derivative transaction if it is permitted to own, invest in, or otherwise have economic exposure to the reference instrument.  Depending on the type of derivative instrument and the Fund’s investment strategy, a reference instrument could be a security, instrument, index, currency, commodity, economic indicator or event (“reference instruments”).  The Fund may engage in derivative transactions for hedging purposes, to seek total return or as a substitute for the purchase or sale of securities.

Derivative instruments are subject to a number of risks, including adverse or unexpected movements in the price of the reference instrument, and counterparty, liquidity, market, tax and leverage risks.  Certain derivatives may also be subject to credit risk and interest rate risk.  In addition, derivatives also involve the risk that changes in their value may not correlate perfectly with the assets, rates, indices or instruments they are designed to hedge or closely track.  Use of derivative instruments may cause the realization of higher amounts of short-term capital gains (generally taxed at ordinary income tax rates) than if such instruments had not been used. Success in using derivative instruments to hedge portfolio assets depends on the degree of price correlation between the derivative instruments and the hedged asset.  Imperfect correlation may be caused by several factors, including temporary price disparities among the trading markets for the derivative instrument, the reference instrument and the Fund’s assets.  To the extent that a derivative instrument is intended to hedge against an event that does not occur, the Fund may realize losses.

OTC derivative instruments involve an additional risk in that the issuer or counterparty may fail to perform its contractual obligations. Some derivative instruments are not readily marketable or may become illiquid under adverse market conditions. In addition, during periods of market volatility, an option or commodity exchange or swap execution facility or clearinghouse may suspend or limit trading in an exchange-traded derivative instrument, which may make the contract temporarily illiquid and difficult to price. Commodity exchanges may also establish daily limits on the amount that the price of a futures contract or futures option can vary from the previous day’s settlement price. Once the daily limit is reached, no trades may be made that day at a price beyond the limit. This may prevent the closing out of positions to limit losses.  The ability to terminate OTC derivative instruments may depend on the cooperation of the counterparties to such contracts. For thinly traded derivative instruments, the only source of price quotations may be the selling dealer or counterparty. In addition, certain provisions of the Code limit the use of derivative instruments.   Derivatives permit the Fund to increase or decrease the level of risk, or change the character of the risk, to which its portfolio is exposed in much the same way as the Fund can increase or decrease the level of risk, or change the character of the risk, of its portfolio by making investments in specific securities.  There can be no assurance that the use of derivative instruments will benefit the Fund.

The U.S. and non-U.S. derivatives markets have undergone substantial changes in recent years as a result of changes under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) in the United States and regulatory changes in Europe, Asia and other non-U.S. jurisdictions.  In particular, the Dodd-Frank Act and related regulations require many derivatives to be margined and/or cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. The SEC adopted Rule 18f-4 under the 1940 Act, which applies to the Fund’s use of derivative investments and certain financing transactions. Among other things, Rule 18f-4 requires certain funds that invest in derivative instruments beyond a specified limited amount (generally greater than 10% of a Fund's net assets) to apply a value-at-risk based limit to their use of certain derivative instruments and financing transactions and to adopt and implement a derivatives risk management program. To the extent a Fund uses derivative instruments (excluding certain currency and interest rate hedging transactions) in a limited amount (up to 10% of a Fund's net assets), it will not be subject to the full requirements of Rule 18f-4. In addition, to the extent that the Fund enters into reverse repurchase agreements or similar financing transactions, the Fund may elect to either treat all of its

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reverse repurchase agreements or similar financing transactions as derivatives transactions for purposes of Rule 18f-4 or comply (with respect to reverse repurchase agreements or similar financing transactions) with the asset segregation requirements under Section 18 of the 1940 Act.  The implementation of these requirements or additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Fund engages in derivative transactions.  Fund management cannot predict the effects of any new governmental regulation that may be implemented, and there can be no assurance that any new government regulation will not adversely affect the Fund’s performance or ability to achieve its investment objective(s).

Residual Interest Bonds.  Residual interest bonds are issued by a trust (the “trust”) that holds municipal obligations. The value of residual interest bonds is derived from the value of such obligations.  The trust also issues floating-rate notes to third parties that may be senior to the residual interest bonds. Residual interest bonds make interest payments to holders of the residual interest that bear an inverse relationship to the interest rate paid on the floating-rate notes. As required by applicable accounting standards, the Fund records interest expense as a liability with respect to floating-rate notes and also records offsetting interest income in an amount equal to this expense. While residual interest bonds create leverage, they do not constitute borrowings for purposes of the Fund’s restrictions on borrowings.

Futures Contracts. Futures are standardized, exchange-traded contracts. Futures contracts on securities obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of the financial instrument called for in the contract at a specified future date at a specified price. An index futures contract obligates the purchaser to take, and a seller to deliver, an amount of cash equal to a specific dollar amount times the difference between the value of a specific index at the close of the last trading day of the contract and the price at which the agreement is made. No physical delivery of the underlying securities in the index is made. It is the practice of holders of futures contracts to close out their positions on or before the expiration date by use of offsetting contract positions, and physical delivery of financial instruments or delivery of cash, as applicable, is thereby avoided.  An option on a futures contract gives the holder the right to enter into a specified futures contract.

Interest Rate Swaps.   Interest rate swaps involve the exchange by the Fund with another party of their respective commitments to pay or receive interest, e.g., an exchange of fixed rate payments for floating-rate payments.

Credit Default Swaps.  Credit default swap agreements (“CDS”) enable the Fund to buy or sell credit protection on an individual issuer or basket of issuers (i.e., the reference instrument).  The Fund may enter into CDS to gain or short exposure to a reference instrument. Long CDS positions are utilized to gain exposure to a reference instrument (similar to buying the instrument) and are akin to selling insurance on the instrument. Short CDS positions are utilized to short exposure to a reference instrument (similar to shorting the instrument) and are akin to buying insurance on the instrument.  

Under a CDS, the protection “buyer” in a credit default contract is generally obligated to pay the protection “seller” an upfront or a periodic stream of payments over the term of the contract, provided that no credit event, such as a default, on a reference instrument has occurred.  If a credit event occurs, the seller generally must pay the buyer the “par value” (full notional value) of the reference instrument in exchange for an equal face amount of the reference instrument described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled.  If the Fund is a buyer and no credit event occurs, the Fund may recover nothing if the swap is held through its termination date.  As a seller, the Fund generally receives an upfront payment or a fixed rate of income throughout the term of the swap provided that there is no credit event.  The Fund’s obligations under a CDS will be accrued daily (offset against any amounts owed to the Fund).

In response to market events, federal and certain state regulators have proposed regulation of the CDS market. These regulations may limit the Fund’s ability to use CDS and/or the benefits of CDS. CDS may be difficult to value and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The Fund may have difficulty, be unable or may incur additional costs to acquire any securities or instruments it is required to deliver under a CDS.  The Fund may have limited ability to eliminate its exposure under a CDS either by assignment or other disposition, or by entering into an offsetting swap agreement.  The Fund also may have limited ability to eliminate its exposure under a CDS if the reference instrument has declined in value.

Total Return Swaps.  A total return swap is a contract in which one party agrees to make periodic payments to another party based on the change in market value of a reference instrument during the specified period, in return for periodic payments from the other party that are based on a fixed or variable interest rate or the total return of the reference instrument or another reference instrument.  Total return swap agreements may be used to obtain exposure to a security or market without owning or taking physical custody of such security or investing directly in such market.

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Options.  Options may be traded on an exchange and OTC. By buying a put option on a particular instrument, the Fund acquires a right to sell the underlying instrument at the exercise price.  By buying a put option on an index, the Fund acquires a right to receive the cash difference between the strike price of the option and the index price at expiration. A purchased put position also typically can be sold at any time by selling at prevailing market prices.  Purchased put options generally are expected to limit the Fund's risk of loss through a decline in the market value of the underlying security or index until the put option expires.  When buying a put option, the Fund pays a premium to the seller of the option.  If the price of the underlying security or index is above the exercise price of the option as of the option valuation date, the option expires worthless and the Fund will not be able to recover the option premium paid to the seller.  The Fund may purchase uncovered put options on securities, meaning it will not own the securities underlying the option.  

The Fund may also write (i.e., sell) put options. The Fund will receive a premium for selling a put option, which may increase the Fund's return. In selling a put option on a security, the Fund has the obligation to buy the security at an agreed upon price if the price of such instrument decreases below the exercise price.  By selling a put option on an index, the Fund has an obligation to make a payment to the buyer to the extent that the value of the index decreases below the exercise price as of the option valuation date.  If the value of the underlying security or index on the option’s expiration date is above the exercise price, the option will generally expire worthless and the Fund, as option seller, will have no obligation to the option holder.

The Fund may purchase call options.  By purchasing a call option on a security, the Fund has the right to buy the security at the option’s exercise price.  By buying a call option on an index, the Fund acquires the right to receive the cash difference between the market price of the index and strike price at expiration.  Call options typically can be exercised any time prior to option maturity or, sold at the prevailing market price.  

The Fund may also write (i.e., sell) a call option on a security or index in return for a premium.  A call written on a security obligates the Fund to deliver the underlying security at the option exercise price.  Written index call options obligate the Fund to make a cash payment to the buyer at expiration if the market price of the index is above the option strike price. Calls typically can also be bought back by the Fund at prevailing market prices and the Fund also may enter into closing purchase transactions with respect to written call options.

The Fund’s options positions are marked to market daily.  The value of options is affected by changes in the value and dividend rates of their underlying instruments, changes in interest rates, changes in the actual or perceived volatility of the relevant index or market and the remaining time to the options’ expiration, as well as trading conditions in the options market.  The hours of trading for options may not conform to the hours during which the underlying instruments are traded.  To the extent that the options markets close before markets for the underlying instruments, significant price and rate movements can take place in the markets that would not be reflected concurrently in the options markets.

The Fund's ability to sell the instrument underlying a call option may be limited while the option is in effect unless the Fund enters into a closing purchase transaction. Uncovered call options have speculative characteristics and are riskier than covered call options because there is no underlying instrument held by the Fund that can act as a partial hedge.  As the seller of a covered call option or an index call option, the Fund may forego, during the option’s life, the opportunity to profit from increases in the market value of the underlying instrument covering the call option above the sum of the premium received by the Fund and the exercise price of the call.  The Fund also retains the risk of loss, minus the option premium received, should the price of the underlying instrument decline.

Participants in OTC markets are typically not subject to the same credit evaluation and regulatory oversight as are members of “exchange-based” markets. OTC option contracts generally carry greater liquidity risk than exchange-traded contracts. This risk may be increased in times of financial stress, if the trading market for OTC options becomes restricted. The ability of the Fund to transact business with any one or a number of counterparties may increase the potential for losses to the Fund, due to the lack of any independent evaluation of the counterparties or their financial capabilities, and the absence of a regulated market to facilitate settlement of the options.

Credit Options.   Credit options are options whereby the purchaser has the right, but not the obligation, to enter into a transaction involving either an asset with inherent credit risk or a credit derivative at terms specified at the inception of the option.  

Credit Linked Notes. A credit linked note (“CLN”) is a type of hybrid instrument in which a special purpose entity issues a structured note (the “note issuer”) with respect to which the reference instrument is a single bond, a portfolio of bonds or the unsecured credit of an issuer, in general (each a “reference credit”). The purchaser of the CLN (the “note purchaser”) invests a par amount and receives a payment during the term of the CLN that equals a fixed or floating rate of interest equivalent to a high rated funded asset (such as a bank certificate of deposit) plus an additional premium that relates to taking on the credit risk of the reference credit. Upon maturity of the CLN, the note purchaser will receive a payment equal to: (i) the original par amount paid to the note issuer, if there is no occurrence

Eaton Vance High Yield Municipal Income Fund14Prospectus dated June 1, 2023 

of a designated event of default, restructuring or other credit event (each a “credit event”) with respect to the issuer of the reference credit; or (ii) the market value of the reference credit, if a credit event has occurred. Depending upon the terms of the CLN, it is also possible that the note purchaser may be required to take physical delivery of the reference credit in the event of a credit event. Most CLNs use a corporate bond (or a portfolio of corporate bonds) as the reference credit. However, almost any type of fixed-income security (including foreign government securities), index or derivative contract (such as a credit default swap) can be used as the reference credit.

Forward Rate Agreements.  Under a forward rate agreement, the Fund locks in an interest rate at a future settlement date. If the interest rate on the settlement date exceeds the lock rate, the Fund pays the seller the difference between the two rates. If the lock rate exceeds the interest rate on the settlement date, the seller pays the Fund the difference between the two rates. Any such gain received by the Fund would be taxable.  These instruments are traded in the OTC market.

Maturity.  Average effective maturity is a weighted average of all the maturities of the Fund’s investments in income securities, computed by weighing each effective maturity date (which takes into account all mortgage prepayments, puts, calls and adjustable coupons) by the market value of the income security.

Pooled Investment Vehicles.  The Fund may invest in pooled investment vehicles to the extent permitted by the 1940 Act, and the rules, regulations and interpretations thereunder.  Pooled investment vehicles are open- and closed-end investment companies unaffiliated with the investment adviser, open-end investment companies affiliated with the investment adviser and exchange-traded funds (“ETFs”). Pooled investment vehicles are subject to the risks of investing in the underlying securities or other instruments that they own.  The market for common shares of certain closed-end investment companies and ETFs, which are generally traded on an exchange and may be traded at a premium or discount to net asset value, is affected by the demand for those securities, regardless of the value of such fund’s underlying securities.  Additionally, natural or environmental disasters, widespread disease or other public health issues, war, acts of terrorism or other events could result in increased premiums or discounts to such fund’s net asset value.  The Fund will indirectly bear its proportionate share of any management fees and other operating expenses paid by unaffiliated and certain affiliated pooled investment vehicles in which it invests.  If such fees exceed 0.01% of the average net assets of the Fund, the costs associated with such investments will be reflected under Acquired Fund Fees and Expenses in the Fund’s Annual Fund Operating Expenses table(s) in its Fund Summary.

Counterparty Risk. A financial institution or other counterparty with whom the Fund does business (such as trading or as a derivative counterparty), or that underwrites, distributes or guarantees any instruments that the Fund owns or is otherwise exposed to, may decline in financial condition and become unable to honor its commitments. This could cause the value of Fund shares to decline or could delay the return or delivery of collateral or other assets to the Fund. Counterparty risk is increased for contracts with longer maturities.

Liquidity Risk.  The Fund is exposed to liquidity risk when trading volume, lack of a market maker, or legal restrictions impair the Fund’s ability to sell particular investments or close derivative positions at an advantageous market price. Trading opportunities are also more limited for securities and other instruments that are not widely held or are traded in less developed markets.  These factors may make it more difficult to sell or buy a security at a favorable price or time. Consequently, the Fund may have to accept a lower price to sell an investment or continue to hold it or keep the position open, sell other investments to raise cash or abandon an investment opportunity, any of which could have a negative effect on the Fund’s performance. It also may be more difficult to value less liquid investments.  These effects may be exacerbated during times of financial or political stress. Increased Fund redemption activity also may increase liquidity risk due to the need of the Fund to sell portfolio investments and may negatively impact Fund performance.

The Fund will not acquire any illiquid investment if, immediately after the acquisition, the Fund will have invested more than 15% of its net assets in illiquid investments.  Illiquid investments mean any investments that the Fund’s investment adviser and/or sub-adviser, as applicable, reasonably expect cannot be sold or disposed of in seven calendar days or less under then-current market conditions without the sale or disposition significantly changing the market value of the investment.

Borrowing.   The Fund is permitted to borrow for temporary purposes (such as to satisfy redemption requests, to remain fully invested in anticipation of expected cash inflows and to settle transactions).  Any borrowings by the Fund are subject to the requirements of the 1940 Act.  Borrowings are also subject to the terms of any credit agreement between the Fund and lender(s).  Fund borrowings may be equal to as much as 331/3% of the value of the Fund’s total assets (including such borrowings) less the Fund’s liabilities (other than borrowings).  The Fund will not purchase additional investments while outstanding borrowings exceed 5% of the value of its total assets.

Eaton Vance High Yield Municipal Income Fund15Prospectus dated June 1, 2023 

In addition, the Fund will be required to maintain a specified level of asset coverage with respect to all borrowings and may be required to sell some of its holdings to reduce debt and restore coverage at times when it may not be advantageous to do so.  The rights of the lender to receive payments of interest and repayments of principal of any borrowings made by the Fund under a credit facility are senior to the rights of holders of shares with respect to the payment of dividends or upon liquidation. In the event of a default under a credit arrangement, the lenders may have the right to cause a liquidation of the collateral (i.e., sell Fund assets) and, if any such default is not cured, the lenders may be able to control the liquidation as well.

Leverage. Certain types of Fund transactions may give rise to economic leverage, which represents a non-cash exposure to the underlying reference instrument. Leverage can increase both the risk and return potential of the Fund.  

The use of leverage may cause the Fund to maintain liquid assets or liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet segregation requirements.  Leverage may cause the Fund’s share price to be more volatile than if it had not been leveraged, as certain types of leverage may exaggerate the effect of any increase or decrease in the value of the Fund’s portfolio securities.  The loss on leveraged investments may substantially exceed the initial investment.

Cash and Money Market Instruments; Temporary Defensive Positions.  The Fund may invest in cash or money market instruments, including high quality short-term instruments or an affiliated investment company that invests in such instruments.  During unusual market conditions, including for temporary defensive purposes, the Fund may invest up to 100% of its assets in cash or money market instruments, which may be inconsistent with its investment objective(s) and other policies, and as such, the Fund may not achieve its investment objective(s) during this period.

Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

Securities Lending.  The Fund may lend its portfolio securities to broker-dealers and other institutional borrowers.  During the existence of a loan, the Fund will continue to receive the equivalent of the interest paid by the issuer on the securities loaned, or all or a portion of the interest on investment of the collateral, if any. The Fund may pay lending fees to such borrowers. Loans will only be made to firms that have been approved by the investment adviser, and the investment adviser or the securities lending agent will periodically monitor the financial condition of such firms while such loans are outstanding. Securities loans will only be made when the investment adviser believes that the expected returns, net of expenses, justify the attendant risks.  Securities loans currently are required to be secured continuously by collateral in cash, cash equivalents (such as money market instruments) or other liquid securities held by the custodian and maintained in an amount at least equal to the market value of the securities loaned.  The Fund may engage in securities lending for total return as well as income, and may invest the collateral received from loans in investments in which the Fund may invest.  Upon return of the loaned securities, the Fund would be required to return the related collateral to the borrower and may be required to liquidate portfolio securities in order to do so.  The Fund may lend up to one-third of the value of its total assets or such other amount as may be permitted by law.

As with other extensions of credit, there are risks of delay in recovery or even loss of rights in the securities loaned if the borrower of the securities fails financially.  To the extent that the portfolio securities acquired with such collateral have decreased in value, it may result in the Fund realizing a loss at a time when it would not otherwise do so. As such, securities lending may introduce leverage into the Fund. The Fund also may incur losses if the returns on securities that it acquires with cash collateral are less than the applicable rebate rates paid to borrowers and related administrative costs.

Restricted Securities.  Securities held by the Fund may be legally restricted as to resale (such as those issued in private placements), including commercial paper issued pursuant to Section 4(a)(2) of the 1933 Act, securities eligible for resale pursuant to Rule 144A thereunder, and securities of U.S. and non-U.S. issuers initially offered and sold outside the United States pursuant to Regulation S thereunder.  Restricted securities may not be listed on an exchange and may have no active trading market.  The Fund may incur additional expense when disposing of restricted securities, including all or a portion of the cost to register the securities.  The Fund also may acquire securities through private placements under which it may agree to contractual restrictions on the resale of such securities that are in addition to applicable legal restrictions.  In addition, if the investment adviser and/or sub-adviser, if applicable, receives non-public information about the issuer, the Fund may as a result be unable to sell the securities.

Restricted securities may be difficult to value properly and may involve greater risks than securities that are not subject to restrictions on resale. It may be difficult to sell restricted securities at a price representing fair value until such time as the securities may be sold publicly.  Under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Fund could find it more difficult to sell such securities when the investment adviser

Eaton Vance High Yield Municipal Income Fund16Prospectus dated June 1, 2023 

and/or sub-adviser, if applicable, believes it advisable to do so or may be able to sell such securities only at prices lower than if such securities were more widely held.  Holdings of restricted securities may increase the level of Fund illiquidity if eligible buyers become uninterested in purchasing them. Restricted securities may involve a high degree of business and financial risk, which may result in substantial losses.

U.S. Treasury and Government Securities.  U.S. Treasury securities (“Treasury Securities”) include U.S. Treasury obligations that differ in their interest rates, maturities and times of issuance.  U.S. Government agency securities (“Agency Securities”) include obligations issued or guaranteed by U.S. Government agencies or instrumentalities and government-sponsored enterprises.  Agency Securities may be guaranteed by the U.S. Government or they may be backed by the right of the issuer to borrow from the U.S. Treasury, the discretionary authority of the U.S. Government to purchase the obligations, or the credit of the agency, instrumentality or enterprise.  

Government-sponsored enterprises, such as the Federal Home Loan Mortgage Corporation (“Freddie Mac”), the Federal National Mortgage Association (“Fannie Mae”), the Federal Home Loan Banks (“FHLBs”), the Private Export Funding Corporation (“PEFCO”), the Federal Deposit Insurance Corporation (“FDIC”), the Federal Farm Credit Banks (“FFCB”) and the Tennessee Valley Authority (“TVA”), although chartered or sponsored by Congress, are not funded by congressional appropriations and the debt and mortgage-backed securities issued by them are neither guaranteed nor issued by the U.S. Government.  Treasury Securities and Agency Securities also include any security or agreement collateralized or otherwise secured by Treasury Securities or Agency Securities, respectively.

Because of their high credit quality and market liquidity, U.S. Treasury and Agency Securities generally provide a lower current return than obligations of other issuers.  While the U.S. Government has provided financial support to Fannie Mae and Freddie Mac in the past, there can be no assurance that it will support these or other government-sponsored enterprises in the future.

To the extent a Fund focuses its investments in securities issued or guaranteed by U.S. government agencies or instrumentalities, any market movements, regulatory changes or changes in political or economic conditions that affect the U.S. government agencies or instrumentalities in which the Fund invests may have a significant impact on the Fund's performance. Events that would adversely affect the market prices of securities issued or guaranteed by one government agency or instrumentality may adversely affect the market price of securities issued or guaranteed by other government agencies or instrumentalities.

Transportation Sector Risk. To the extent the Fund invests a substantial portion of its assets in the transportation sector, factors that have an adverse impact on this sector may have a disproportionate impact on the Fund’s performance. The transportation sector can be affected by local and global economic conditions such as the price and availability of fuel, oil, and gas; government regulation; labor relations; operating and equipment costs; disruptive weather and environmental effects; mass casualty accidents; technological developments and disruptions; insurance costs; industry competition; and acts of war or terrorism that damage transportation systems. As a result, the value of the Fund’s shares may fluctuate more than that of a fund that does not invest significantly in companies in the transportation sector.

Cybersecurity Risk.  With the increased use of technologies by Fund service providers to conduct business, such as the Internet, the Fund is susceptible to operational, information security and related risks. The Fund relies on communications technology, systems, and networks to engage with clients, employees, accounts, shareholders, and service providers, and a cyber incident may inhibit the Fund’s ability to use these technologies. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber attacks include, but are not limited to, gaining unauthorized access to digital systems (e.g., through “hacking” or malicious software coding) for purposes of misappropriating assets or sensitive information, corrupting data, or causing operational disruption. Cyber attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites. A denial-of-service attack is an effort to make network services unavailable to intended users, which could cause shareholders to lose access to their electronic accounts, potentially indefinitely. Employees and service providers also may not be able to access electronic systems to perform critical duties for the Fund, such as trading and NAV calculation, during a denial-of-service attack. There is also the possibility for systems failures due to malfunctions, user error and misconduct by employees and agents, natural disasters, or other foreseeable and unforeseeable events.

Because technology is consistently changing, new ways to carry out cyber attacks are always developing. Therefore, there is a chance that some risks have not been identified or prepared for, or that an attack may not be detected, which puts limitations on the Fund's ability to plan for or respond to a cyber attack. Similar types of cybersecurity risks also are present for issuers of securities in which the Fund invests, which could have material adverse consequences for those issuers and result in a decline in the market price of their securities. Furthermore, as a result of cyber attacks, technological disruptions, malfunctions or failures, an exchange or market may close or suspend trading in specific securities or the entire market, which could prevent the Fund from, among other things, buying or selling the Fund or

Eaton Vance High Yield Municipal Income Fund17Prospectus dated June 1, 2023 

accurately pricing its securities. Like other funds and business enterprises, the Fund and its service providers have experienced, and will continue to experience, cyber incidents consistently. In addition to deliberate cyber attacks, unintentional cyber incidents can occur, such as the inadvertent release of confidential information by the Fund or its service providers.

The Fund uses third party service providers who are also heavily dependent on computers and technology for their operations. Cybersecurity failures by or breaches of the Fund’s investment adviser or administrator and other service providers (including, but not limited to, the custodian or transfer agent), and the issuers of securities in which the Fund invests, may disrupt and otherwise adversely affect their business operations. This may result in financial losses to the Fund, impede Fund trading, interfere with the Fund’s ability to calculate its NAV, limit a shareholder’s ability to purchase or redeem shares of the Fund or cause violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, litigation costs, or additional compliance costs. While many of the Fund’s service providers have established business continuity plans and risk management systems intended to identify and mitigate cyber attacks, there are inherent limitations in such plans and systems, including the possibility that certain risks have not been identified. The Fund cannot control the cybersecurity plans and systems put in place by service providers to the Fund and issuers in which the Fund invests.  The Fund and its shareholders could be negatively impacted as a result.

Research Process.  The Fund’s portfolio management utilizes information provided by, and the expertise of, the research staff of the investment adviser and/or certain of its affiliates in making investment decisions. As part of the research process, portfolio management may consider financially material environmental, social and governance (“ESG”) factors. Such factors, alongside other relevant factors, may be taken into account in the Fund’s securities selection process.

Geopolitical Risk.  The increasing interconnectivity between global economies and markets increases the likelihood that events or conditions in one country, region, sector, industry or market or, with respect to one company, may adversely impact issuers in a different country, region, sector, industry or market. For example, adverse developments in the banking or financial services sector could impact companies operating in various sectors or industries and adversely impact the Fund’s investments. Securities in the Fund’s portfolio may underperform due to inflation (or expectations for inflation), interest rates, global demand for particular products or resources, natural disasters, health emergencies (such as epidemics and pandemics), terrorism, regulatory events and governmental or quasi-governmental actions. The occurrence of global events similar to those in recent years, such as terrorist attacks around the world, natural disasters, health emergencies, social and political discord, war, banking or debt crises and downgrades, among others, may result in market volatility and may have long term effects on both the U.S. and global financial markets. Other financial, economic and other global market and social developments or disruptions may result in similar adverse circumstances, and it is difficult to predict when similar events affecting the U.S. or global financial markets may occur, the effects that such events may have and the duration of those effects (which may last for extended periods).

Such global events may negatively impact broad segments of businesses and populations, cause a significant negative impact on the performance of the Fund’s investments, adversely affect and increase the volatility of the Fund’s share price, and/or exacerbate pre-existing political, social and economic risks to the Fund. The Fund’s operations may be interrupted and any such event(s) could have a significant adverse impact on the value and risk profile of the Fund’s portfolio. There is a risk that you may lose money by investing in the Fund.

Recent Market Conditions.  The outbreak of COVID-19 and efforts to contain its spread have resulted in closing borders, enhanced health screenings, changes to healthcare service preparation and delivery, quarantines, cancellations, disruptions to supply chains and customer activity, as well as general concern and uncertainty. The impact of this coronavirus, and the effects of other infectious illness outbreaks, epidemics or pandemics, may be short term or may continue for an extended period of time. Health crises caused by outbreaks of disease, such as the coronavirus outbreak, may exacerbate other pre-existing political, social and economic risks and disrupt normal market conditions and operations. For example, a global pandemic or other widespread health crisis could cause substantial market volatility and exchange trading suspensions and closures.  In addition, the increasing interconnectedness of markets around the world may result in many markets being affected by events or conditions in a single country or region or events affecting a single or small number of issuers. The coronavirus outbreak and public and private sector responses thereto have led to large portions of the populations of many countries working from home for indefinite periods of time, temporary or permanent layoffs, disruptions in supply chains, and lack of availability of certain goods. The impact of such responses could adversely affect the information technology and operational systems upon which the Fund and the Fund’s service providers rely, and could otherwise disrupt the ability of the employees of the Fund’s service providers to perform critical tasks relating to the Fund. Any such impact could adversely affect the Fund’s performance, or the performance of the securities in which the Fund invests and may lead to losses on your investment in the Fund.

Eaton Vance High Yield Municipal Income Fund18Prospectus dated June 1, 2023 

Tax-Sensitive Investing. The Fund may hold a security to achieve more favorable tax treatment or sell a security to create tax losses. The Fund’s ability to utilize various tax-management techniques may be curtailed or eliminated by tax legislation or regulation.  The Fund may not be able to minimize taxable distributions to shareholders and a portion of the Fund’s distributions may be taxable.

Converting to Hub and Spoke Structure. The Fund may invest all of its assets in an open-end management investment company (“portfolio”) with substantially the same investment objective, policies and restrictions as the Fund. Any such portfolio would be advised by the Fund’s investment adviser (or an affiliate) and the Fund would not pay directly any advisory fee with respect to the assets so invested. The Fund may initiate investments in a portfolio at any time without shareholder approval.

General.  The Fund's 80% Policy only may be changed with shareholder approval.  Unless otherwise stated, the Fund's investment objective and certain other policies may be changed without shareholder approval.  Shareholders will be given 60 days' advance written notice of any material change in the investment objective. The Fund might not use all of the strategies and techniques or invest in all of the types of securities described in this Prospectus or the SAI.  While at times the Fund may use alternative investment strategies in an effort to limit its losses, it may choose not to do so.

The Fund’s annual operating expenses are expressed as a percentage of the Fund’s average daily net assets and may change as Fund assets increase and decrease over time.  Purchase and redemption activities by Fund shareholders may impact the management of the Fund and its ability to achieve its investment objective.   In addition, the redemption by one or more large shareholders or groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund.  Mutual funds, investment advisers, other market participants and many securities markets are subject to rules and regulations and the jurisdiction of one or more regulators.  Changes to applicable rules and regulations or to widely accepted market conventions or standards could have an adverse effect on securities markets and market participants, as well as on the Fund’s ability to execute its investment strategy.  With the increased use of technologies by Fund service providers, such as the Internet, to conduct business, the Fund is susceptible to operational, information security and related risks.  See “Additional Information about Investment Strategies and Risks” in the Fund’s SAI.

Management and Organization

Management. The Fund’s investment adviser is Boston Management and Research (“BMR”).  BMR is an indirect wholly owned subsidiary of Morgan Stanley. BMR, a registered investment adviser, has offices at Two International Place, Boston, MA 02110.  Eaton Vance Management (“Eaton Vance”), BMR, and their predecessor organizations have been managing assets since 1924 and managing mutual funds since 1931.

Morgan Stanley (NYSE: MS), whose principal offices are at 1585 Broadway, New York, New York 10036, is a preeminent global financial services firm engaged in securities trading and brokerage activities, as well as providing investment banking, research and analysis, financing and financial advisory services.  As of March 31, 2023, Morgan Stanley’s asset management operations had aggregate assets under management of approximately $1.4 trillion.

The Fund’s semiannual report covering the fiscal period ended July 31 provides information regarding the basis for the Trustees’ approval of the Fund’s investment advisory agreement.

The investment adviser manages the investments of the Fund.  Under its investment advisory agreement with the Fund, BMR receives a monthly advisory fee equal to the aggregate of a daily asset based fee and a daily income based fee.  The fees are applied on the basis of the following categories:

On January 31, 2023, the Fund had net assets of $1,197,693,620.  For the fiscal year ended January 31, 2023, the effective annual rate of investment advisory fee paid to BMR, based on average daily net assets of the Fund, was  0.43%.

Eaton Vance High Yield Municipal Income Fund19Prospectus dated June 1, 2023 

The investment adviser has agreed to reimburse the total amount of advisory fees paid by Class W shares. This expense reimbursement will continue through May 31, 2024.  Any amendment to or termination of this reimbursement would require approval of the Board of Trustees.  

Cynthia J. Clemson and William J. Delahunty, Jr. are the portfolio managers of the Fund. Ms. Clemson has been a portfolio manager of the Fund since September 2004 and Mr. Delahunty has been a portfolio manager of the Fund since October 2021.  Ms. Clemson is a Vice President of Eaton Vance and BMR and has managed other Eaton Vance portfolios and been an employee of the Eaton Vance organization for more than five years.  Mr. Delahunty is a Vice President of Eaton Vance and BMR and has managed other Eaton Vance portfolios and been an employee of the Eaton Vance organization for more than five years.

The SAI provides additional information about each portfolio manager’s compensation, other accounts managed by each portfolio manager, and each portfolio manager’s ownership of Fund shares.

Eaton Vance serves as the administrator of the Fund, providing the Fund with administrative services and related office facilities.  Eaton Vance does not currently receive a fee for serving as administrator.

Eaton Vance provides sub-transfer agency and related services to Eaton Vance mutual funds pursuant to a Sub-Transfer Agency Support Services Agreement.  For its services under the agreement, Eaton Vance receives an aggregate fee from such funds equal to its actual expenses incurred in performing such services.

Organization. The Fund is a series of Eaton Vance Municipals Trust II, a Massachusetts business trust.  The Fund offers multiple classes of shares.  Each Class represents a pro rata interest in the Fund but is subject to different expenses and rights.  The Fund does not hold annual shareholder meetings but may hold special meetings for matters that require shareholder approval (such as electing or removing Trustees, approving management or advisory contracts or changing investment policies that may only be changed with shareholder approval).

Valuing Shares

You may buy or sell (redeem) shares of the Fund at the NAV next determined for the class after receipt of your order in good order, plus any applicable sales charge. The Fund’s NAV is determined as of the close of the New York Stock Exchange (“NYSE”) (normally 4:00 p.m. Eastern Time) on each day that the NYSE is open for business (typically Monday through Friday) (the “Pricing Time”). The Fund is closed for business and will not issue a NAV on the following business holidays and any other business day that the NYSE is closed: New Year’s Day, Martin Luther King, Jr. Day, Presidents’ Day, Good Friday, Memorial Day, Juneteenth, Independence Day, Labor Day, Thanksgiving Day and Christmas Day.  On holidays or other days when the NYSE is closed, the NAV is generally not calculated and the Fund generally does not transact purchase or redemption requests.  However, on those days, the value of the Fund’s assets may be affected to the extent that the Fund holds foreign securities that trade on foreign markets that are open.  In addition, trading of securities that are primarily listed on foreign exchanges may take place on weekends and other days when the Fund does not price its interests or transact purchase or redemption requests.

If the NYSE is closed due to inclement weather, technology problems or any other reason on a day it would normally be open for business, or the NYSE has an unscheduled early closing on a day it has opened for business, the Fund reserves the right to treat such day as a business day and accept purchase and redemption orders until, and calculate its NAV as of, the normally scheduled close of regular trading on the NYSE for that day, so long as its investment adviser believes there generally remains an adequate market to obtain reliable and accurate market quotations. If market quotations, official closing prices, or information furnished by a pricing service are not readily available or, in the investment adviser’s opinion, are deemed unreliable for a security, then that security will be fair valued in good faith by the investment adviser in accordance with applicable fair value pricing policies and in accordance with applicable law. The Fund may elect to remain open and price its shares on days when the NYSE is closed but the primary securities markets on which the Fund’s securities trade remain open. Therefore, to the extent, if any, that the Fund invests in securities primarily listed on foreign exchanges, the value of the Fund’s portfolio securities may change on days when you will not be able to purchase or sell your shares. When purchasing or redeeming Fund shares through a financial intermediary, your financial intermediary must receive your order by the close of regular trading on the NYSE in order for the purchase price or the redemption price to be based on that day’s net asset value per share. It is the financial intermediary’s responsibility to transmit orders promptly. The Fund may accept purchase and redemption orders as of the time of their receipt by certain financial intermediaries (or their designated intermediaries).

The Board has adopted procedures for valuing investments (the “Procedures”) and has delegated to the investment adviser(s), as valuation designee, the daily valuation of such investments. Pursuant to the Procedures, securities and other investments held by the Fund for which market quotations are readily available are generally valued at market value. Exchange-listed investments (including certain derivatives) are normally valued at last sale or closing prices.  Exchange-

Eaton Vance High Yield Municipal Income Fund20Prospectus dated June 1, 2023 

traded options are valued at the mean of the bid and asked prices at valuation time as reported by the Options Price Reporting Authority for U.S. listed options, or by the relevant exchange or board of trade for non-U.S. listed options.  Non-exchange traded derivatives are normally valued on the basis of quotes obtained from brokers and dealers or independent pricing services.  Most loans and other debt obligations are valued using prices supplied by one or more pricing services.

Pursuant to the Procedures, if market quotations are not readily available (or otherwise not reliable) for a particular investment, the fair value of the investment will be determined by the investment adviser(s), as valuation designee. A market quotation is readily available only when that quotation is a quoted price (unadjusted) in active markets for identical investments that the Fund can access at the measurement date, provided that a quotation will not be readily available if it is not reliable. As such, the Fund will use fair value pricing if, for example, market prices or a pricing service's prices (as applicable) are unavailable or deemed unreliable, or if events occur after the close of a securities market (usually a foreign market) and before portfolio assets are valued that cause or are likely to cause a market quotation to be unavailable or unreliable, such as corporate actions, regulatory news, or natural disasters or governmental actions that may affect investments in a particular sector, country or region.  An investment that is fair valued may be valued at a price higher or lower than (i) actual market quotations, (ii) the value determined by other funds using their own fair valuation procedures, or (iii) the price at which the investment could have been sold during the period in which fair valuation was used with respect to such investment to calculate the Fund’s NAV.  Eaton Vance has established a Valuation Committee that oversees the valuation of investments.

Purchasing Shares

The Fund may suspend the sale of its shares at any time and any purchase order may be refused for any reason.  The U.S. registered funds sponsored by the Eaton Vance organization (the “Eaton Vance funds”) generally do not accept investments from residents of the European Union, the United Kingdom or Switzerland.  The Eaton Vance funds also do not accept investments from other non-U.S. residents, provided that a fund may accept investments from certain non-U.S. investors at the discretion of the principal underwriter.  The Fund does not issue share certificates.

As used throughout this Prospectus, the term “employer sponsored retirement plan” includes the following: an employer sponsored pension or profit sharing plan that qualifies under section 401(a) of the Code (such as a 401(k) plan, money purchase pension, profit sharing and defined benefit plan); ERISA covered 403(b) plan; Taft-Hartley multi-employer plan; and non-qualified deferred compensation arrangements that operate in a similar manner to a qualified retirement plan (including 457 plans and executive deferred compensation arrangements). Individual Retirement Accounts (“IRAs”) are not employer sponsored retirement plans for purposes of this definition.

Class W Shares

Class W shares are available for purchase only at the direction of the investment adviser or one of its affiliates on behalf of investors that are eligible clients of the investment adviser or its affiliates that have entered into a separate investment management or advisory agreement pursuant to which such clients pay an investment management or advisory fee, including investment vehicles that are sponsored, managed, advised or sub-advised by the investment adviser or its affiliates (such investment adviser or affiliate, an “account adviser”). There is no minimum initial purchase amount for Class W shares.

Purchase orders for Class W shares must be submitted by an account adviser to the applicable financial intermediary. For more information about purchasing Class W shares, please contact the account adviser.  

Subsequent Investments. Requests to make additional investments must be made directly to the account adviser. There is no minimum subsequent investment amount.

Inactive Accounts.  In accordance with state “unclaimed property” (also known as “escheatment”) laws, your Fund shares may legally be considered abandoned and required to be transferred to the relevant state if no account activity or contact with the Fund or your financial intermediary occurs within a specified period of time.  Please initiate contact a least once per calendar year and maintain a current and valid mailing address on record for your account.  For more information, please see https://funds.eatonvance.com/mutual-funds-and-abandoned-property.php  or please contact us at 1-800-262-1122.

Restrictions on Excessive Trading and Market Timing.  The Fund is not intended for excessive trading or market timing.  Market timers seek to profit by rapidly switching money into a fund when they expect the share price of the fund to rise and taking money out of the fund when they expect those prices to fall.  By realizing profits through short-term trading, shareholders that engage in rapid purchases and sales (including exchanges, if permitted) of a fund’s shares may dilute the value of shares held by long-term shareholders. Volatility resulting from excessive purchases and sales of fund shares, especially involving large dollar amounts, may disrupt efficient portfolio management.  In particular, excessive

Eaton Vance High Yield Municipal Income Fund21Prospectus dated June 1, 2023 

purchases and sales of a fund’s shares may cause a fund to have difficulty implementing its investment strategies, may force the fund to sell portfolio securities at inopportune times to raise cash or may cause increased expenses (such as increased brokerage costs, realization of taxable capital gains without attaining any investment advantage or increased administrative costs).

A fund that invests in securities that are, among other things, thinly traded, traded infrequently or illiquid, is susceptible to the risk that the current market price for such securities may not accurately reflect current market values.  A shareholder may seek to engage in short-term trading to take advantage of these pricing differences (commonly referred to as “price arbitrage”).  The investment adviser is authorized to use the fair value of a security if prices are unavailable or are deemed unreliable (see “Valuing Shares”).  The use of fair value pricing and the restrictions on excessive trading and market timing described below are intended to reduce a shareholder’s ability to engage in price arbitrage to the detriment of the Fund.

The Boards of the Eaton Vance funds have adopted policies to discourage short-term trading and market timing and to seek to minimize their potentially detrimental effects (the “Policy”).  Under the Policy, the Board has delegated to Eaton Vance the responsibility to reject or cancel a purchase order, suspend or terminate an exchange privilege or terminate the ability of a shareholder to invest in the Eaton Vance funds if Eaton Vance determines that a proposed transaction involves market timing or excessive trading that it believes is likely to be detrimental to the Fund.

Pursuant to the Policy, two “round-trips” completed by a Fund shareholder within 90 days through one or more accounts (the “Limitation”) generally will be deemed to be indicative of market timing or trading excessively in fund shares.  A “round trip” is defined as a purchase or exchange into a fund followed or preceded by a redemption or exchange out of the fund.  Purchases and redemptions subject to the Limitation include those made by exchanging to or from another fund. Eaton Vance will evaluate transactions in Fund shares that violate the Limitation to determine whether they are likely to be detrimental to the Fund. In making such a determination, Eaton Vance may consider various factors, such as the amount, frequency and nature of trading activity. If such a determination is made, the Fund shareholder may be subject to restrictions on trading Fund shares, as described above.  Eaton Vance uses reasonable efforts to detect market timing and excessive trading activity that is likely to be detrimental to the Fund, but it cannot ensure that it will be able to identify all such cases.  Eaton Vance may also reject or cancel any purchase order (including an exchange) from a shareholder or group of shareholders for any other reason.  In applying the Policy, and in particular when determining whether a transaction is likely to be detrimental to the Fund, Eaton Vance will be required to make judgments that are inherently subjective and will depend on the specific facts and circumstances. Such determinations will be made in a manner believed to be in the best interest of the Fund’s shareholders.  No Eaton Vance fund has any arrangement to permit market timing.

The following fund share transactions generally are exempt from the Policy because they generally do not raise market timing or excessive trading concerns:  

·transactions (i) made pursuant to the Fund’s systematic purchase, exchange or redemption plan, (ii) made as the result of automatic reinvestment of dividends or distributions, or (iii) initiated by the Fund (e.g., for transactions due to a failure to meet applicable account minimums); 

·transactions made by participants in employer sponsored retirement plans involving (i) participant payroll or employer contributions or loan repayments, (ii) redemptions as part of plan terminations or at the direction of the plan, mandatory retirement distributions, or (iii) rollovers;  

·transactions in shares of Eaton Vance Short Duration Government Income Fund; or 

·investments in a fund by ReFlow in connection with the ReFlow liquidity program (if applicable to the Fund, the ReFlow liquidity program is described under “Investment Objectives & Principal Policies and Risks” above). 

The following Fund share transactions generally are exempt from the Limitation; however, these transactions are subject to monitoring by Eaton Vance and may be subject to restrictions if deemed likely to be detrimental to the Fund:

·transactions made by model-based discretionary advisory accounts; or 

·transactions made by funds that invest in the Fund as part of an asset reallocation in accordance with their investment policies or in response to Fund inflows and outflows.  

It may be difficult for Eaton Vance to identify market timing or excessive trading in omnibus accounts traded through financial intermediaries.  Eaton Vance has provided guidance to financial intermediaries (such as banks, broker-dealers, insurance companies and retirement administrators) concerning the application of the Policy to Fund shares held in omnibus accounts maintained and administered by such intermediaries, including guidance concerning situations where market timing or excessive trading is considered to be detrimental to the Fund.  Eaton Vance may rely on a financial intermediary’s policy to restrict market timing and excessive trading if it believes that policy is likely to prevent market

Eaton Vance High Yield Municipal Income Fund22Prospectus dated June 1, 2023 

timing that is likely to be detrimental to the Fund.  Such policy may be more or less restrictive than the Policy.  Although Eaton Vance reviews trading activity at the omnibus account level for activity that indicates potential market timing or excessive trading activity, Eaton Vance typically will not request or receive individual account data unless suspicious trading activity is identified.  Eaton Vance generally relies on financial intermediaries to monitor trading activity in omnibus accounts in good faith in accordance with their own policies or the Policy.  Eaton Vance cannot ensure that these financial intermediaries will in all cases apply the Policy or their own policies, as the case may be, to accounts under their control.

Choosing a Share Class.  This Prospectus offers Class W shares of the Fund. The Fund also offers Class A, Class C and Class I shares through another prospectus.

Class W shares are available for purchase only at the direction of an account adviser on behalf of investors that are eligible clients of the investment adviser or its affiliates that have entered into a separate investment management or advisory agreement pursuant to which such clients pay an investment management or advisory fee, including investment vehicles that are sponsored, managed, advised or sub-advised by the investment adviser or its affiliates. Class W shares are not subject to a sales charge and do not pay distribution or service fees. In addition, no sub-accounting or other similar fees, or any finder’s fee payments are charged or paid on Class W shares.

Payments to Financial Intermediaries. The principal underwriter, out of its own resources, may make cash payments to certain financial intermediaries (which may include affiliates of the principal underwriter and investment adviser) who provide marketing support, transaction processing and/or administrative services and, in some cases, include some or all Eaton Vance funds in preferred or specialized selling programs.  Payments made by the principal underwriter to a financial intermediary may be significant and are typically in the form of fees based on Fund sales, assets, transactions processed and/or accounts attributable to that financial intermediary.  Financial intermediaries also may receive amounts from the principal underwriter in connection with educational or due diligence meetings that include information concerning Eaton Vance funds.  The principal underwriter may pay or allow other promotional incentives or payments to financial intermediaries to the extent permitted by applicable laws and regulations.  

As used in this Prospectus, the term “financial intermediary” includes any broker, dealer, bank (including bank trust departments), registered investment adviser, financial planner, a retirement plan and/or its administrator, their designated intermediaries and any other firm having a selling, administration or similar agreement with the principal underwriter or its affiliates.

Redeeming Shares

An account adviser must submit redemption orders for Class W shares to the applicable financial intermediary. Class W shares may be held only by eligible investors and cannot be exchanged for any other share class. The Fund reserves the right to redeem shares of any investor if the investor ceases to be an eligible investor. Each shareholder, by participating in a managed account program that purchases Fund shares, agrees to the redemption of such Fund shares upon termination of its participation in such program. Shares of the Fund will be redeemed at the NAV next determined after a redemption request is received in good order. The redemption of Fund shares will have tax consequences. For more information about redeeming shares, please contact the account adviser.

Redemption proceeds typically are paid to the redeeming shareholder in cash up to two business days after the redemption, but payment could take up to seven days, as permitted by the 1940 Act for the reasons discussed below.  The actual number of days following receipt of a redemption request in which the Fund typically expects to pay redemption proceeds generally will depend on how you hold your shares with the Fund.  

If your shares are held in a “street name” account with a financial intermediary (see “Shareholder Account Features – ‘Street Name’ Accounts”), your intermediary will elect through National Securities Clearing Corporation (“NSCC”) to settle redemptions either one business day or two business days after the redemption date and redemption proceeds normally will be wired to your financial intermediary on the settlement date pursuant to that election.  

The Fund typically expects to meet redemption requests by (i) distributing any cash holdings, (ii) selling portfolio investments and/or (iii) borrowing from a bank under a line of credit.  In addition to the foregoing, the Fund also may distribute securities as payment (a so-called “redemption in-kind”), in which case the redeeming shareholder may pay fees and commissions to convert the securities to cash.  Unless requested by a shareholder, the Fund generally expects to limit use of redemption in-kind to stressed market conditions, but reserves the right to do so at any time. For Class W shares, requests to receive redemption proceeds in-kind must be made directly to the account adviser. The Fund may decline a shareholder's request to receive redemption proceeds in-kind. Securities distributed in a redemption in-kind would be valued pursuant to the Fund’s valuation procedures and selected by the investment adviser. If a shareholder receives securities in a redemption in-kind, the shareholder could incur brokerage or other charges in converting the securities to cash and the value of such securities would be subject to price fluctuations until sold.  There can be no

Eaton Vance High Yield Municipal Income Fund23Prospectus dated June 1, 2023 

assurance that the Fund will manage liquidity successfully in all market environments. As a result, the Fund may not be able to pay redemption proceeds in a timely fashion because of unusual market conditions, an unusually high volume of redemption requests or other factors.  Additional information about redemptions in-kind, including the procedures for submitting such redemption requests, is contained in the Fund’s SAI.

If your account value falls below $750, you may be asked either to add to your account or redeem it within 60 days.  If you take no action, your account will be redeemed at net asset value and the proceeds sent to you.

Shareholder Account Features

Distributions.  Subject to the policies of your financial intermediary, you may have your Fund distributions paid in one of the following ways:

Information about the Fund.  From time to time, you may receive the following:

·Semiannual and annual reports containing a list of portfolio holdings as of the end of the second and fourth fiscal quarters, respectively, performance information and financial statements. 

·Periodic account statements, showing recent activity and total share balance. 

·Tax information needed to prepare your income tax returns. 

·Proxy materials, in the event a shareholder vote is required. 

·Special notices about significant events affecting your Fund. 

Most fund information (including semiannual and annual reports, prospectuses and proxy statements) as well as your periodic account statements can be delivered electronically.  For more information please go to www.eatonvance.com/edelivery.

The Eaton Vance funds have established policies and procedures with respect to the disclosure of portfolio holdings and other information concerning Fund characteristics.  A description of these policies and procedures is provided below and additionally in the SAI.  Such policies and procedures regarding disclosure of portfolio holdings are designed to prevent the misuse of material, non-public information about the funds.

The Fund will file information regarding its portfolio holdings with the SEC on its Form N-PORT.  The Fund’s annual and semiannual reports (as filed on Form N-CSR) and certain information filed on Form N-PORT may be viewed on the SEC’s website (www.sec.gov).  The most recent fiscal quarter-end holdings may also be viewed on the Eaton Vance website (www.eatonvance.com).  Portfolio holdings information that is filed with the SEC is posted on the Eaton Vance website approximately 60 days after the end of the quarter to which it relates.  Portfolio holdings information as of each month end is posted to the website approximately one month after such month end.  The Fund also posts information about certain portfolio characteristics (such as top ten holdings and asset allocation) at least quarterly on the Eaton Vance website approximately ten business days after the period and the Fund may also post performance attribution as of a month end or more frequently if deemed appropriate.

Exchange Privilege.  Class W shares may not be exchanged for any other share class.

“Street Name” Accounts.  If your shares are held in a “street name” account at a financial intermediary, that intermediary (and not the Fund or its transfer agent) will perform all recordkeeping, transaction processing and distribution payments.  Because the Fund does not maintain an account for you, you should contact your financial intermediary to make changes in your account, or obtain account information.  You will not be able to utilize a number of shareholder features, such as telephone or internet transactions, directly with the Fund and certain features may be subject to different requirements.  If you transfer shares in a “street name” account to an account with another financial intermediary, you should obtain historical information about your shares prior to the transfer.  If you fail to provide your full account history to your new financial intermediary following a transfer, you may be ineligible for certain features of the Fund.  

Procedures for Opening New Accounts.  To help the government fight the funding of terrorism and money laundering activities, federal law requires financial institutions to obtain, verify and record information that identifies each new customer who opens an account with the Fund and to determine whether such person’s name appears on government

Eaton Vance High Yield Municipal Income Fund24Prospectus dated June 1, 2023 

lists of known or suspected terrorists or terrorist organizations.  When you open an account, the transfer agent or your financial intermediary will ask you for your name, address, date of birth (for individuals), residential or business street address (although post office boxes are still permitted for mailing) and social security number, taxpayer identification number, or other government-issued identifying number.  You also may be asked to produce a copy of your driver’s license, passport or other identifying documents in order to verify your identity.  In addition, it may be necessary to verify your identity by cross-referencing your identification information with a consumer report or other electronic databases.  Other information or documents may be required to open accounts for corporations and other entities.  Federal law prohibits the Fund and other financial institutions from opening a new account unless they receive the minimum identifying information described above.  If a person fails to provide the information requested, any application by that person to open a new account will be rejected.  Moreover, if the transfer agent or the financial intermediary is unable to verify the identity of a person based on information provided by that person, it may take additional steps including, but not limited to, requesting additional information or documents from the person, closing the person’s account or reporting the matter to the appropriate federal authorities.  If your account is closed for this reason, your shares may be automatically redeemed at the net asset value next determined.  If the Fund’s net asset value has decreased since your purchase, you will lose money as a result of this redemption.  The Fund has also designated an anti-money laundering compliance officer.

Account Questions.  If you have any questions about your account or the services available, please contact the account adviser.

Potential Conflicts of Interest

As a diversified global financial services firm, Morgan Stanley, the parent company of the investment adviser, engages in a broad spectrum of activities, including financial advisory services, investment management activities, lending, commercial banking, sponsoring and managing private investment funds, engaging in broker-dealer transactions and principal securities, commodities and foreign exchange transactions, research publication and other activities. In the ordinary course of its business, Morgan Stanley is a full-service investment banking and financial services firm and therefore engages in activities where Morgan Stanley’s interests or the interests of its clients may conflict with the interests of a Fund or Portfolio, as applicable (collectively, for purposes of this section, “Fund” or “Funds”). Morgan Stanley advises clients and sponsors, manages or advises other investment funds and investment programs, accounts and businesses (collectively, together with any new or successor Morgan Stanley funds, programs, accounts or businesses, (other than funds, programs, accounts or businesses sponsored, managed, or advised by former direct or indirect subsidiaries of Eaton Vance Corp. (“Eaton Vance Investment Accounts”)), the “MS Investment Accounts,” and, together with the Eaton Vance Investment Accounts, the ‘‘Affiliated Investment Accounts’’) with a wide variety of investment objectives that in some instances may overlap or conflict with a Fund’s investment objectives and present conflicts of interest. In addition, Morgan Stanley or the investment adviser may also from time to time create new or successor Affiliated Investment Accounts that may compete with a Fund and present similar conflicts of interest. The discussion below enumerates certain actual, apparent and potential conflicts of interest. There is no assurance that conflicts of interest will be resolved in favor of Fund shareholders and, in fact, they may not be. Conflicts of interest not described below may also exist.

The discussions below with respect to actual, apparent and potential conflicts of interest also may be applicable to or arise from the MS Investment Accounts whether or not specifically identified.  For more information about conflicts of interest, see the section entitled “Potential Conflicts of Interest” in the SAI.

Material Non-public Information. It is expected that confidential or material non-public information regarding an investment or potential investment opportunity may become available to the investment adviser. If such information becomes available, the investment adviser may be precluded (including by applicable law or internal policies or procedures) from pursuing an investment or disposition opportunity with respect to such investment or investment opportunity. Morgan Stanley has established certain information barriers and other policies to address the sharing of information between different businesses within Morgan Stanley. In limited circumstances, however, including for purposes of managing business and reputational risk, and subject to policies and procedures and any applicable regulations, Morgan Stanley personnel, including personnel of the investment adviser, on one side of an information barrier may have access to information and personnel on the other side of the information barrier through “wall crossings.” The investment adviser faces conflicts of interest in determining whether to engage in such wall crossings. Information obtained in connection with such wall crossings may limit or restrict the ability of the investment adviser to engage in or otherwise effect transactions on behalf of the Fund(s) (including purchasing or selling securities that the investment adviser may otherwise have purchased or sold for a Fund in the absence of a wall crossing).

Investments by Morgan Stanley and its Affiliated Investment Accounts. In serving in multiple capacities to Affiliated Investment Accounts, Morgan Stanley, including the investment adviser  and its investment teams, may have obligations to other clients or investors in Affiliated Investment Accounts, the fulfillment of which may not be in the best interests of a

Eaton Vance High Yield Municipal Income Fund25Prospectus dated June 1, 2023 

Fund or its shareholders. A Fund’s investment objectives may overlap with the investment objectives of certain Affiliated Investment Accounts. As a result, the members of an investment team may face conflicts in the allocation of investment opportunities among a Fund and other investment funds, programs, accounts and businesses advised by or affiliated with the investment adviser. Certain Affiliated Investment Accounts may provide for higher management or incentive fees or greater expense reimbursements or overhead allocations, all of which may contribute to this conflict of interest and create an incentive for the investment adviser to favor such other accounts. To seek to reduce potential conflicts of interest and to attempt to allocate such investment opportunities in a fair and equitable manner, the investment adviser has implemented allocation policies and procedures. These policies and procedures are intended to give all clients of the investment adviser, including the Fund(s), fair access to investment opportunities consistent with the requirements of organizational documents, investment strategies, applicable laws and regulations, and the fiduciary duties of the investment adviser.

Investments by Separate Investment Departments. The entities and individuals that provide investment-related services for the Fund and certain other Eaton Vance Investment Accounts (the “Eaton Vance Investment Department”) may be different from the entities and individuals that provide investment-related services to MS Investment Accounts (the “MS Investment Department” and, together with the Eaton Vance Investment Department, the “Investment Departments”). Although Morgan Stanley has implemented information barriers between the Investment Departments in accordance with internal policies and procedures, each Investment Department may engage in discussions and share information and resources with the other Investment Department on certain investment-related matters. A MS Investment Account could trade in advance of a Fund (and vice versa), might complete trades more quickly and efficiently than a Fund, and/or achieve different execution than a Fund on the same or similar investments made contemporaneously, even when the Investment Departments shared research and viewpoints that led to that investment decision. Any sharing of information or resources between the Investment Department servicing the Fund and the MS Investment Department may result, from time to time, in a Fund simultaneously or contemporaneously seeking to engage in the same or similar transactions as an account serviced by the other Investment Department and for which there are limited buyers or sellers on specific securities, which could result in less favorable execution for the Fund than such account.

Payments to Broker-Dealers and Other Financial Intermediaries. The investment adviser and/or Eaton Vance Distributors, Inc. (“EVD”) may pay compensation, out of their own funds and not as an expense of a Fund, to certain financial intermediaries (which may include affiliates of the investment adviser and EVD), including recordkeepers and administrators of various deferred compensation plans, in connection with the sale, distribution, marketing and retention of shares of the Fund and/or shareholder servicing. The prospect of receiving, or the receipt of, additional compensation, as described above, by financial intermediaries may provide such financial intermediaries and their financial advisors and other salespersons with an incentive to favor sales of shares of a Fund over other investment options with respect to which these financial intermediaries do not receive additional compensation (or receive lower levels of additional compensation). These payment arrangements, however, will not change the price that an investor pays for shares of a Fund or the amount that the Fund receives to invest on behalf of an investor. Investors may wish to take such payment arrangements into account when considering and evaluating any recommendations relating to Fund shares and should review carefully any disclosures provided by financial intermediaries as to their compensation. In addition, in certain circumstances, the investment adviser may restrict, limit or reduce the amount of a Fund’s investment, or restrict the type of governance or voting rights it acquires or exercises, where the Fund (potentially together with Morgan Stanley) exceeds a certain ownership interest, or possesses certain degrees of voting or control or has other interests.

Morgan Stanley Trading and Principal Investing Activities. Notwithstanding anything to the contrary herein, Morgan Stanley will generally conduct its sales and trading businesses, publish research and analysis, and render investment advice without regard for a Fund’s holdings, although these activities could have an adverse impact on the value of one or more of the Fund’s investments, or could cause Morgan Stanley to have an interest in one or more portfolio investments that is different from, and potentially adverse to, that of a Fund.

Morgan Stanley’s Investment Banking and Other Commercial Activities. Morgan Stanley advises clients on a variety of mergers, acquisitions, restructuring, bankruptcy and financing transactions. Morgan Stanley may act as an advisor to clients, including other investment funds that may compete with a Fund and with respect to investments that a Fund may hold. Morgan Stanley may give advice and take action with respect to any of its clients or proprietary accounts that may differ from the advice given, or may involve an action of a different timing or nature than the action taken, by a Fund. Morgan Stanley may give advice and provide recommendations to persons competing with a Fund and/or any of a Fund’s investments that are contrary to the Fund’s best interests and/or the best interests of any of its investments. Morgan Stanley’s activities on behalf of its clients (such as engagements as an underwriter or placement agent) may restrict or otherwise limit investment opportunities that may otherwise be available to a Fund.

Eaton Vance High Yield Municipal Income Fund26Prospectus dated June 1, 2023 

Morgan Stanley may be engaged to act as a financial advisor to a company in connection with the sale of such company, or subsidiaries or divisions thereof, may represent potential buyers of businesses through its mergers and acquisition activities and may provide lending and other related financing services in connection with such transactions. Morgan Stanley’s compensation for such activities is usually based upon realized consideration and is usually contingent, in substantial part, upon the closing of the transaction. Under these circumstances, a Fund may be precluded from participating in a transaction with or relating to the company being sold or participating in any financing activity related to the merger or acquisition.

General Process for Potential Conflicts. All of the transactions described above involve the potential for conflicts of interest between the investment adviser, related persons of the investment adviser and/or their clients. The Investment Advisers Act of 1940, as amended (the “Advisers Act”), the 1940 Act and ERISA impose certain requirements designed to decrease the possibility of conflicts of interest between an investment adviser and its clients. In some cases, transactions may be permitted subject to fulfillment of certain conditions. Certain other transactions may be prohibited. In addition, the investment adviser has instituted policies and procedures designed to prevent conflicts of interest from arising and, when they do arise, to ensure that it effects transactions for clients in a manner that is consistent with its fiduciary duty to its clients and in accordance with applicable law. The investment adviser seeks to ensure that potential or actual conflicts of interest are appropriately resolved taking into consideration the overriding best interests of the client.

Additional Tax Information

The Fund declares distributions daily and ordinarily pays distributions monthly.  Different classes may distribute different amounts.  Your account will be credited with distributions beginning on the business day after the day when the funds used to purchase your Fund shares are collected by the transfer agent.  For tax purposes, the entire monthly distribution of the Fund’s daily distributions ordinarily will constitute income to you that is exempt from federal income tax.  The Fund intends to distribute net realized capital gains (if any) annually.  The exemption of “exempt-interest dividend” income from regular U.S. federal income taxation does not necessarily result in similar exemptions of such income under state or local tax laws.  It may also be necessary, in order to qualify for favorable tax treatment and to avoid any Fund-level tax, for the Fund to make a special income and/or capital gains distribution at the end of the calendar year.

The net investment income of certain U.S. individuals, estates and trusts is subject to a 3.8% Medicare contribution tax.  For individuals, the tax is on the lesser of the “net investment income” and the excess of modified adjusted gross income over $200,000 (or $250,000 if married filing jointly).  Net investment income includes, among other things, interest, dividends (other than exempt-interest dividends), gross income and capital gains derived from passive activities and trading in securities or commodities.  Net investment income is reduced by deductions “properly allocable” to this income.

Any recognized gain or income attributable to market discount on long-term tax-exempt municipal obligations (i.e., obligations with a term of more than one year) generally is taxable as ordinary income to the extent the gain or income does not exceed the “accrued market discount” on such obligation.  A long-term debt obligation is generally treated as acquired at a market discount if purchased after its original issue at a price less than (i) the stated principal amount payable at maturity, in the case of an obligation that does not have original issue discount or (ii) in the case of an obligation that does have original issue discount, the sum of the issue price and any original issue discount that accrued before the Fund purchased the obligation, in both cases, subject to a de minimis exclusion.

The Fund may invest a portion of its assets in securities that generate income that is not exempt from federal income tax.  The rate of taxes on distributions of capital gains are determined by how long the Fund owned (or is treated as having owned) the investments that generated them, rather than how long a shareholder has owned his or her shares in the Fund.  Distributions of taxable investment income and net short-term capital gains will generally be taxable as ordinary income.  Distributions of net gains from investments held for more than one year are generally taxable as long-term capital gains.  Distributions of interest on certain municipal obligations are a tax preference item under the AMT provisions applicable to individuals.  The Fund’s distributions will be treated as described above for federal income tax purposes regardless of whether they are paid in cash or reinvested in additional shares.  A redemption of Fund shares, including an exchange for shares of another fund, is generally a taxable transaction.

The Fund may be required to withhold, for U.S. federal income tax purposes, a portion of the dividends, distributions and redemption proceeds payable to shareholders who fail to provide the Fund with their correct taxpayer identification number or make required certifications, or who have been notified by the Internal Revenue Service (“IRS”) that they are subject to backup withholding. Certain shareholders are exempt from backup withholding. Backup withholding is not an additional tax and any amount withheld may be credited against a shareholder’s U.S. federal income tax liability.

Eaton Vance High Yield Municipal Income Fund27Prospectus dated June 1, 2023 

Certain foreign entities may be subject to a 30% withholding tax on ordinary dividend income paid under the Foreign Account Tax Compliance Act (“FATCA”).  To avoid withholding, foreign financial institutions subject to FATCA must agree to disclose to the relevant revenue authorities certain information regarding their direct and indirect U.S. owners and other foreign entities must certify certain information regarding their direct and indirect U.S. owners to the Fund.  In addition, the IRS and the Department of the Treasury have issued proposed regulations providing that these withholding rules will not be applicable to the gross proceeds of share redemptions or capital gain dividends the Fund pays.  For more detailed information regarding FATCA withholding and compliance, please refer to the SAI.

Shareholders, particularly corporations, recipients of social security or railroad retirement benefits and those subject to the AMT, should consult with their tax advisors concerning the applicability of federal, state, local and other taxes to an investment.

Eaton Vance High Yield Municipal Income Fund28Prospectus dated June 1, 2023 

Financial Highlights

The financial highlights are intended to help you understand the Fund’s financial performance for the period(s) indicated. Certain information in the table reflects the financial results for a single Fund share.  The total returns in the table represent the rate an investor would have earned (or lost) on an investment in the Fund (assuming reinvestment of all distributions at net asset value).  This information has been audited by Deloitte & Touche LLP, an independent registered public accounting firm.  The report of Deloitte & Touche LLP and the Fund’s financial statements are incorporated by reference into the Fund's SAI and included in the Fund’s annual report, which is available upon request.

(1)For the period from the commencement of operations, October 1, 2021, to January 31, 2022. 

(2)Computed using average shares outstanding. 

(3)Returns are historical and are calculated by determining the percentage change in net asset value with all distributions reinvested. 

(4)The investment adviser reimbursed the total amount of the advisory fees paid (equal to 0.43% and 0.37% of average daily net assets for the year ended January 31, 2023 and the period ended January 31, 2022, respectively). Absent this reimbursement, total return would be lower. 

(5)Not annualized. 

(6)Annualized. 

(7)Interest and fee expense relates to the liability for floating rate notes issued in conjunction with residual interest bond transactions (see Note 1H) to the Fund's audited financial statements. 

(8)For the year ended January 31, 2022. 

Eaton Vance High Yield Municipal Income Fund29Prospectus dated June 1, 2023 

More Information

About the Fund:  More information is available in the Statement of Additional Information.  The Statement of Additional Information is incorporated by reference into this Prospectus.  Additional information about the Fund’s investments is available in the annual and semiannual reports (collectively, the “reports”).  In the annual report, you will find a discussion of the market conditions and investment strategies that significantly affected the Fund’s performance during the past fiscal year.  You may obtain free copies of the Statement of Additional Information and the reports on Eaton Vance’s website at www.eatonvance.com or by contacting the principal underwriter:

Eaton Vance Distributors, Inc.
Two International Place
Boston, MA  02110
1-800-262-1122
website: www.eatonvance.com

Information about the Fund (including the Statement of Additional Information and reports) is available on the EDGAR database on the SEC’s website at www.sec.gov, and copies of this information may be obtained, after paying a duplicating fee, by electronic request at the following email address: [email protected].

As permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s annual and semi-annual shareholder reports are no longer being sent by mail unless you specifically request paper copies of the reports. Instead, the reports are being made available on the Funds’ website (http://www.eatonvance.com/funddocuments), and you will be notified each time a report is posted and provided with a website address to access the report. You may elect to receive all future Fund shareholder reports in paper free of charge at any time. Holders of Class W shares must contact their financial intermediary to elect to continue to receive paper copies of Fund shareholder reports or to sign up for electronic delivery of shareholder reports and other communications.

Shareholder Inquiries: You can obtain more information from Eaton Vance Shareholder Services or the Fund transfer agent, BNY Mellon Investment Servicing (US) Inc., by writing or calling:

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