CXE MFS High Income Municipal Trust

Manag ement

Investment manager: Legg Mason Partners Fund Advisor, LLC

Subadviser: Western Asset Management Company

Investment professionals: Stephen A. Walsh, Robert E. Amodeo, David T. Fare and Dennis J. McNamara. Mr. Fare has been a part of the portfolio management team for the fund since the fund’s inception. Messrs. Walsh and Amodeo have been a part of the portfolio management team for the fund since 2007. Mr. McNamara has been a part of the portfolio management team for the fund since 2012. These investment professionals work together with a broader investment management team. It is anticipated that Mr. Walsh will step down as a member of the fund’s portfolio management team effective on or about March 31, 2014 and that S. Kenneth Leech will join the fund’s portfolio management team at that time.

Purcha se and sale of fund shares

You may purchase, redeem or exchange shares of the fund each day the New York Stock Exchange is open, at the fund’s net asset value determined after receipt of your request in good order, subject to any applicable sales charge.

The fund’s initial and subsequent investment minimums generally are set forth in the accompanying table:

Your financial intermediary may impose different investment minimums.

For more information about how to purchase, redeem or exchange shares, and to learn which classes of shares are available to you, you should contact your financial intermediary, or, if you hold your shares or plan to purchase shares through the fund, you should contact the fund by phone at 1-877-721-1926 or by mail at Legg Mason Funds, P.O. Box 55214, Boston, MA 02205-8504.

Tax inform ation

The fund intends to distribute income that is generally exempt from regular federal income tax. A portion of the fund’s distributions may be subject to such tax and/or to the federal alternative minimum tax.

Payments to broke r/dealers and other financial intermediaries

The fund’s related companies may pay broker/dealers or other financial intermediaries (such as a bank or an insurance company) for the sale of fund shares, shareholder services and other purposes. These payments create a conflict of interest by influencing your broker/dealer or other intermediary or its employees or associated persons to recommend the fund over another investment. Ask your financial adviser or salesperson or visit your financial intermediary’s or salesperson’s website for more information.

More o n the fund’s investment strategies, investments and risks

The fund seeks to generate high current income exempt from regular federal income tax while preserving capital.

Under normal circumstances, the fund invests at least 80% of its assets in municipal securities and in participation or other interests in municipal securities issued by banks, insurance companies or other financial institutions.

The fund’s 80% policy may not be changed without a shareholder vote.

Except for this policy, the fund’s investment strategies may be changed without shareholder approval. The fund’s investment objective may be changed by the Board of Trustees (the ”Board”) without shareholder approval and on notice to shareholders.

Municipal securities

Municipal securities include debt obligations issued by any of the 50 states or their political subdivisions, agencies and public authorities, certain other governmental issuers (such as Puerto Rico, the U.S. Virgin Islands and Guam) and other qualifying issuers, and investments with similar economic characteristics, the income from which is exempt from regular federal income tax. Although municipal securities are issued by qualifying issuers, payments of principal and interest on municipal securities may be derived solely from revenues from certain facilities, mortgages or private industries, and may not be backed by the issuers themselves. These securities include participation or other interests in municipal securities issued or backed by banks, insurance companies and other financial institutions.

Municipal securities include general obligation bonds, revenue bonds, housing authority bonds, private activity bonds, industrial development bonds, residual interest bonds, tender option bonds, tax and revenue anticipation notes, bond anticipation notes, tax-exempt commercial paper, municipal leases, participation certificates and custodial receipts. General obligation bonds are backed by the full faith and credit of the issuing entity. Revenue bonds are typically used to fund particular projects, such as those relating to education, health care, transportation and utilities, that are expected to produce income sufficient to make the payments on the bonds, since they are not backed by the full taxing power of the municipality. Housing authority bonds are used primarily to fund low to middle income residential projects and may be backed by the payments made on the underlying mortgages. Tax and revenue anticipation notes are generally issued in order to finance short-term cash needs or, occasionally, to finance construction. Tax and revenue anticipation notes are expected to be repaid from taxes or designated revenues in the related period, and they may or may not be general obligations of the issuing entity. Bond anticipation notes are issued with the expectation that their principal and interest will be paid out of proceeds from renewal notes or bonds and may be issued to finance such items as land acquisition, facility acquisition and/or construction and capital improvement projects.

Municipal securities include municipal lease obligations, which are undivided interests issued by a state or municipality in a lease or installment purchase contract which generally relates to equipment or facilities. In some cases, payments under municipal leases do not have to be made unless money is specifically approved for that purpose by an appropriate legislative body.

The fund may invest more than 25% of its assets in municipal securities that derive income from similar types of projects or that are otherwise related in such a way that an economic, business or political development or change affecting one of the securities would also affect the others.

The fund purchases municipal securities, the interest on which, in the opinion of bond counsel at the time the securities are issued, is exempt from regular federal income tax. There is no guarantee that this opinion is correct, and there is no assurance that the Internal Revenue Service (the “IRS”) will agree with bond counsel’s opinion. If the IRS determines that an issuer of a municipal security has not complied with applicable requirements, interest from the security could become subject to regular federal income tax, possibly retroactively to the date the security was issued, and the value of the security could decline significantly and a portion of the distributions to fund shareholders could be recharacterized as taxable. Future litigation or legislation could adversely affect the tax treatment of municipal securities held by the fund.

Some of the fund’s income distributions may be, and distributions of any gains generally will be, subject to regular federal income tax. Some of the fund’s income that is exempt from regular federal income tax may be subject to the federal alternative minimum tax. In addition, distributions of the fund’s income and capital gains will generally be subject to state and local income taxes.

Subject to the fund’s 80% policy, the fund may purchase other securities whose interest is subject to regular federal income tax.

Maturity and duration

The fund may invest in securities of any maturity. The maturity of a fixed income security is a measure of the time remaining until the final payment on the security is due.

The fund normally maintains a dollar-weighted average effective duration of three years or less as estimated by the fund’s subadviser. If the fund’s effective duration falls outside of this range, the fund will take action to bring it within its expected range within a reasonable period of time.

Effective duration seeks to measure the expected sensitivity of market price to changes in interest rates, taking into account the anticipated effects of structural complexities (for example, some bonds can be prepaid by the issuer). The assumptions that are made about a security’s features and options when calculating effective duration may prove to be incorrect. As a result, investors should be aware that effective duration is not an exact measurement and may not reliably predict a security’s price sensitivity to changes in yield or interest rates.

Credit quality

The fund focuses on securities rated investment grade (that is, securities rated in the Baa/BBB categories or above, or, if unrated, determined to be of comparable credit quality by the subadviser). The fund may invest up to 20% of its assets in securities rated below investment grade, or, if unrated, determined to be below investment grade by the subadviser. Below investment grade securities are commonly referred to as ”junk bonds.”

If a security is rated by multiple nationally recognized statistical rating organizations (“NRSROs”) and receives different ratings, the fund will treat the security as being rated in the highest rating category received from an NRSRO. Rating categories may include sub-categories or gradations indicating relative standing.

Derivatives

The fund may engage in a variety of transactions using derivatives, such as futures, options, swaps (including credit default swaps) and warrants. Derivatives are financial instruments whose value depends upon, or is derived from, the value of something else, such as one or more underlying investments, indexes or currencies. Derivatives may be used by the fund for any of the following purposes:

The fund from time to time may sell protection on debt securities by entering into credit default swaps. In these transactions, the fund is generally required to pay the par (or other agreed-upon) value of a referenced debt security to the counterparty in the event of a default on or downgrade of the debt security and/or a similar credit event. In return, the fund receives from the counterparty a periodic stream of payments over the term of the contract. If no default occurs, the fund keeps the stream of payments and has no payment obligations. As the seller, the fund would effectively add leverage to its portfolio because, in addition to its net assets, the fund would be subject to investment exposure on the par (or other agreed-upon) value it had undertaken to pay. Credit default swaps may also be structured based on an index or the debt of a basket of issuers, rather than a single issuer, and may be customized with respect to the default event that triggers purchase or other factors (for example, a particular number of defaults within a basket, or defaults by a particular combination of issuers within the basket, may trigger a payment obligation).

Using derivatives, especially for non-hedging purposes, may involve greater risks to the fund than investing directly in securities, particularly as these instruments may be very complex and may not behave in the manner anticipated by the fund. Certain derivative transactions may have a leveraging effect on the fund.

Use of derivatives or similar instruments may have different tax consequences for the fund than an investment in the underlying security, and such differences may affect the amount, timing and character of income distributed to shareholders, including the proportion of income consisting of exempt-interest dividends.

When the fund enters into derivative transactions, it may be required to segregate assets, or enter into offsetting positions, in accordance with applicable regulations. Such segregation will not limit the fund’s exposure to loss, however, and the fund will have investment risk with respect to both the derivative itself and the assets that have been segregated to cover the fund’s derivative exposure. If the segregated assets represent a large portion of the fund’s portfolio, this may impede portfolio management or the fund’s ability to meet redemption requests or other current obligations.

As noted above, instead of, and/or in addition to, investing directly in particular securities, the fund may use derivatives, such as credit default swaps and futures contracts, synthetic instruments and other instruments that are intended to provide economic exposure to a security, an issuer, an index or basket of securities, or a market. The fund may use one or more types of these instruments without limit, except that these instruments are taken into account when determining compliance with the fund’s 80% policy.

The fund’s subadviser may choose not to make use of derivatives.

More on the fund’s investment strategies, investments and risks cont’d

Other fixed income securities

Subject to the fund’s 80% policy, the fund may purchase fixed income securities that pay interest that is subject to regular federal income tax. Fixed income securities represent obligations of corporations, governments and other entities to repay money borrowed, usually at the maturity of the security. These securities may pay fixed, variable or floating rates of interest. However, some fixed income securities, such as zero coupon bonds, do not pay current interest but are issued at a discount from their face values. Other debt instruments, such as certain mortgage-backed and other asset-backed securities, make periodic payments of interest and/or principal. Some debt instruments are partially or fully secured by collateral supporting the payment of interest and principal. “Fixed income securities” are commonly referred to as “notes,” “debt,” “debt obligations,” “debt securities,” “corporate debt,” “bonds” and “corporate bonds,” and these terms are used in this Prospectus interchangeably, and, where used, are not intended to be limiting.

Variable and floating rate securities

Variable rate securities reset at specified intervals, while floating rate securities reset whenever there is a change in a specified index rate. In most cases, these reset provisions reduce the impact of changes in market interest rates on the value of the security. However, the value of these securities may decline if their interest rates do not rise as much, or as quickly, as other interest rates. Conversely, these securities will not generally increase in value if interest rates decline. The fund may also invest in inverse floating rate debt instruments (“inverse floaters”). An inverse floater may exhibit greater price volatility than a fixed rate obligation of similar credit quality.

Structured instruments

The fund may invest in various types of structured instruments, including securities that have demand, tender or put features, or interest rate reset features. These may include instruments issued by structured investment or special purpose vehicles or conduits, and may be asset-backed or mortgage-backed securities. Structured instruments may take the form of participation interests or receipts in underlying securities or other assets, and in some cases are backed by a financial institution serving as a liquidity provider. Some of these instruments may have an interest rate swap feature which substitutes a floating or variable interest rate for the fixed interest rate on an underlying security. Structured instruments are a type of derivative instrument and the payment and credit qualities of these instruments derive from the assets embedded in the structure. For structured securities that have embedded leverage features, small changes in interest or prepayment rates may cause large and sudden price movements. Structured instruments are often subject to heightened liquidity risk.

Zero coupon, pay-in-kind and deferred interest securities

Zero coupon, pay-in-kind and deferred interest securities may be used by issuers to manage cash flow and maintain liquidity. Zero coupon securities pay no interest during the life of the obligation but are issued at prices below their stated maturity value. Because zero coupon securities pay no interest until maturity, their prices may fluctuate more than other types of securities with the same maturity in the secondary market. However, zero coupon bonds are useful as a tool for managing duration.

Pay-in-kind securities have a stated coupon, but the interest is generally paid in the form of obligations of the same type as the underlying pay-in-kind securities (e.g. bonds) rather than in cash. These securities are more sensitive to the credit quality of the underlying issuer and their secondary market prices may fluctuate more than other types of securities with the same maturity.

Deferred interest securities are obligations that generally provide for a period of delay before the regular payment of interest begins and are issued at a significant discount from face value.

Certain zero coupon, pay-in-kind and deferred interest securities are subject to tax rules applicable to debt obligations acquired with “original issue discount.” The fund would generally have to accrue income on these securities for federal income tax purposes before it receives corresponding cash payments. Because the fund intends to make sufficient annual distributions of its taxable income, including accrued non-cash income, in order to maintain its federal income tax status and avoid fund-level income and excise taxes, the fund might be required to liquidate portfolio securities at a disadvantageous time, or borrow cash, to make these distributions.

When-issued securities, delayed delivery, to be announced and forward commitment transactions

The fund may purchase securities under arrangements (called when-issued, delayed delivery, to be announced or forward commitment basis) where the securities will not be delivered or paid for immediately. The fund will set aside assets to pay for these securities at the time of the agreement. Such transactions involve a risk of loss if the value of the securities declines prior to the settlement date or if the assets set aside to pay for these securities decline in value prior to the settlement date. Therefore, these transactions may have a leveraging effect on the fund, making the value of an investment in the fund more volatile and increasing the fund’s overall investment exposure. Typically, no income accrues on securities the fund has committed to purchase prior to the time delivery of the securities is made, although the fund may earn income on securities it has set aside to cover these positions.

Short-term investments

The fund may invest in cash, money market instruments and short-term securities, including repurchase agreements, U.S. government securities, bank obligations and commercial paper. A repurchase agreement is a transaction in which the fund purchases a security from a seller, subject to the obligation of the seller to repurchase that security from the fund at a higher price. The repurchase agreement thereby determines the yield during the fund’s holding period, while the seller’s obligation to repurchase is secured by the value of the underlying security held by the fund.

Borrowings and reverse repurchase agreements

The fund may enter into borrowing transactions. Borrowing may make the value of an investment in the fund more volatile and increase the fund’s overall investment exposure. The fund may be required to liquidate portfolio securities at a time when it would be disadvantageous to do so in order to make payments with respect to any borrowings. Interest on any borrowings will be a fund expense and will reduce the value of the fund’s shares.

The fund may enter into reverse repurchase agreements, which have characteristics like borrowings. In a reverse repurchase agreement, the fund sells securities to a counterparty, in return for cash, and the fund agrees to repurchase the securities at a later date and for a higher price, representing the cost to the fund for the cash received.

Credit downgrades and other credit events

Credit rating or credit quality of a security is determined at the time of purchase. If, after purchase, the credit rating on a security is downgraded or the credit quality deteriorates, or if the duration of a security is extended, the subadviser will decide whether the security should be held or sold. Upon the occurrence of certain triggering events or defaults on a security held by the fund, or if an obligor of such a security has difficulty meeting its obligations, the fund may obtain a new or restructured security or underlying assets. In that case, the fund may become the holder of securities or other assets that it could not purchase or might not otherwise hold (for example, because they are of lower quality or are subordinated to other obligations of the issuer) at a time when those assets may be difficult to sell or can be sold only at a loss. In addition, the fund may incur expenses in an effort to protect the fund’s interest in securities experiencing these events.

Defensive investing

The fund may depart from its principal investment strategies in response to adverse market, economic or political conditions by taking temporary defensive positions, including by investing in any type of taxable money market instruments and short-term debt securities or holding cash without regard to any percentage limitations. Although the subadviser has the ability to take defensive positions, it may choose not to do so for a variety of reasons, even during volatile market conditions.

Other investments

The fund may also use other strategies and invest in other securities that are described, along with their risks, in the SAI. However, 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 in the SAI. New types of mortgage-backed and asset-backed securities, derivative instruments, hedging instruments and other securities or instruments are developed and marketed from time to time. Consistent with its investment limitations, the fund may invest in new types of securities and instruments.

Percentage and other limitations

For purposes of the fund’s limitations expressed as a percentage of assets or net assets, the term “assets” means net assets plus the amount of any borrowings for investment purposes. The fund’s compliance with its investment limitations and requirements is usually determined at the time of investment. If a percentage limitation is complied with at the time of an investment, any subsequent change in percentage resulting from a change in values or assets, or a change in credit quality, will not constitute a violation of that limitation.

Selection process

The subadviser selects securities that it believes have strong credit quality and are attractively priced. These may include investments with unusual features or privately placed issues that are not widely followed in the fixed income marketplace. In selecting individual securities, the subadviser:

More on the fund’s investment strategies, investments and risks cont’d

More on risks of investing in the fund

Market and interest rate risk. The market prices of fixed income and other securities owned by the fund may go up or down, sometimes rapidly or unpredictably. If the market prices of the securities owned by the fund fall, the value of your investment in the fund will decline. The value of a security may fall due to general market conditions, such as real or perceived adverse economic or political conditions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets or adverse investor sentiment.

Changes in market conditions will not typically have the same impact on all types of securities. The value of a security may also fall due to specific conditions that affect a particular sector of the securities market or a particular issuer.

The market prices of securities may fluctuate significantly when interest rates change. When interest rates rise, the value of fixed income securities, and therefore the value of your investment in the fund, generally goes down. Interest rates have been historically low and are expected to rise. Generally, the longer the maturity or duration of a fixed income security, the greater the impact of a rise in interest rates on the security’s value. However, calculations of duration and maturity may be based on estimates and may not reliably predict a security’s price sensitivity to changes in interest rates. Moreover, securities can change in value in response to other factors, such as credit risk. In addition, different interest rate measures (such as short- and long-term interest rates and U.S. and foreign interest rates), or interest rates on different types of securities or securities of different issuers, may not necessarily change in the same amount or in the same direction. When interest rates go down, the fund’s yield will decline. Also, when interest rates decline, investments made by the fund may pay a lower interest rate, which would reduce the income received by the fund.

Recent market events risk. The global financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities and unprecedented volatility in the markets. Some events that have contributed to ongoing and systemic market risks include the falling values of some sovereign debt and related investments, scarcity of credit and high public debt. In response to the crisis, the U.S. government and the Federal Reserve, as well as certain foreign governments and their central banks have taken steps to support financial markets, including by keeping interest rates at historically low levels. More recently, the Federal Reserve has reduced its market support activities. Further reduction or withdrawal of this support, failure of efforts in response to the crisis, or investor perception that such efforts are not succeeding could negatively affect financial markets generally as well as result in higher interest rates, increase market volatility and reduce the value and liquidity of certain securities.

This environment could make identifying investment risks and opportunities especially difficult for the subadviser, and whether or not the fund invests in securities of issuers located in or with significant exposure to countries experiencing economic and financial difficulties, the value and liquidity of the fund’s investments may be negatively affected. In addition, policy and legislative changes in the United States and in other countries are affecting many aspects of financial regulation. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time.

Credit risk. If an obligor (such as the issuer itself or a party offering credit enhancement) for a security held by the fund fails to pay, otherwise defaults, is perceived to be less creditworthy, becomes insolvent or files for bankruptcy, a security’s credit rating is downgraded or the credit quality or value of any underlying assets declines, the value of your investment in the fund could decline. If the fund enters into financial contracts (such as certain derivatives, repurchase agreements, reverse repurchase agreements, and when-issued, delayed delivery and forward commitment transactions), the fund will be subject to the credit risk presented by the counterparty. In particular, the number of municipal insurers is relatively small, and, as a result, changes in the financial condition of an individual municipal insurer may affect the overall municipal market. In addition, the fund may incur expenses in an effort to protect the fund’s interests or to enforce its rights. Credit risk is broadly gauged by the credit ratings of the securities in which the fund invests. However, ratings are only the opinions of the companies issuing them and are not guarantees as to quality. Securities rated in the lowest category of investment grade (Baa/BBB) may possess certain speculative characteristics.

The fund is subject to greater levels of credit risk to the extent it holds below investment grade debt securities (that is, securities rated below the Baa/BBB categories or unrated securities of comparable quality), or “junk bonds”. These securities have a higher risk of issuer default because, among other reasons, issuers of junk bonds often have more debt in relation to total capitalization than issuers of investment grade securities. These securities are considered speculative, tend to be less liquid and are more difficult to value than higher rated securities and may involve major risk of exposure to adverse conditions and negative sentiments. These securities may be in default or in danger of default as to principal and interest. Unrated securities of comparable quality share these risks.

The fund may invest in securities which are subordinated to more senior securities of the issuer, or which represent interests in pools of such subordinated securities. The fund is more likely to suffer a credit loss on subordinated securities than on non-subordinated securities of the same issuer. If there is a default, bankruptcy or liquidation of the issuer, most subordinated securities are paid only if sufficient assets remain after payment of the issuer’s non-subordinated securities. In addition, any recovery of interest or principal may take more time. As a result, even a perceived decline in creditworthiness of the issuer is likely to have a greater impact on subordinated securities.

Derivatives risk. Derivatives involve special risks and costs and may result in losses to the fund. Using derivatives can increase losses and reduce opportunities for gains when market prices, interest rates or currencies, or the derivatives themselves, behave in a way not anticipated by the fund, especially in abnormal market conditions. Using derivatives also can have a leveraging effect (which may increase investment losses) and increase fund volatility, which is the degree to which the fund’s share price may fluctuate within a short time period. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. The other parties to certain derivatives transactions present the same types of credit risk as issuers of fixed income securities. Derivatives also tend to involve greater liquidity risk and they may be difficult to value. The fund may be unable to terminate or sell its derivative positions. In fact, many over-the-counter derivatives will not have liquidity beyond the counterparty to the instrument. The fund’s use of derivatives may also increase the amount of taxes payable by shareholders. The U.S. government is in the process of adopting and implementing regulations governing derivatives markets, including mandatory clearing of certain derivatives, margin, and reporting requirements. The ultimate impact of the regulations remains unclear. Additional regulation of derivatives may make them more costly, may limit their availability, may disrupt markets or may otherwise adversely affect their value or performance. The fund may be exposed to additional risks as a result of the additional regulations. The extent and impact of the additional regulations are not yet fully known and may not be for some time.

Investments by the fund in structured securities, a type of derivative, raise certain tax, legal, regulatory and accounting issues that may not be presented by direct investments in securities. These issues could be resolved in a manner that could hurt the performance of the fund.

Swap agreements tend to shift the fund’s investment exposure from one type of investment to another. For example, the fund may enter into interest rate swaps, which involve the exchange of interest payments by the fund with another party, such as an exchange of floating rate payments for fixed interest rate payments with respect to a notional amount of principal. If an interest rate swap intended to be used as a hedge negates a favorable interest rate movement, the investment performance of the fund would be less than what it would have been if the fund had not entered into the interest rate swap.

Credit default swap contracts involve heightened risks and may result in losses to a fund. Credit default swaps may be illiquid and difficult to value, and they increase credit risk since a fund has exposure to both the issuer whose credit is the subject of the swap and the counterparty to the swap. The absence of a central exchange or market for swap transactions may lead, in some instances, to difficulties in trading and valuation, especially in the event of market disruptions. Recent legislation requires certain swaps to be executed through a centralized exchange or regulated facility and be cleared through a regulated clearinghouse. Although this clearing mechanism is generally expected to reduce counterparty credit risk, it may disrupt or limit the swap market and may not result in swaps being easier to trade or value. As swaps become more standardized, the fund may not be able to enter into swaps that meet its investment needs. The fund also may not be able to find a clearinghouse willing to accept a swap for clearing. In a cleared swap, a central clearing organization will be the counterparty to the transaction. The fund will assume the risk that the clearinghouse may be unable to perform its obligations.

The fund will be required to maintain its positions with a clearing organization through one or more clearing brokers. The clearing organization will require the fund to post margin and the broker may require the fund to post additional margin to secure the fund’s obligations. The amount of margin required may change from time to time. In addition, cleared transactions may be more expensive to maintain than over-the-counter transactions and may require the fund to deposit larger amounts of margin. The fund may not be able to recover margin amounts if the broker has financial difficulties. Also, the broker may require the fund to terminate a derivatives position under certain circumstances. This may cause the fund to lose money.

Risks associated with the use of derivatives are magnified to the extent that an increased portion of the fund’s assets are committed to derivatives in general or are invested in just one or a few types of derivatives.

Leveraging risk. The value of your investment may be more volatile if the fund borrows or uses derivatives or other investments that have a leveraging effect on the fund’s portfolio. Other risks also will be compounded. This is because leverage generally magnifies the effect of a change in the value of an asset and creates a risk of loss of value on a larger pool of assets than the fund would otherwise have had. The fund may also have to sell assets at inopportune times to satisfy its obligations. The use of leverage is considered to be a speculative investment practice and may result in the loss of a substantial amount, and possibly all, of the fund’s assets.

Liquidity risk. Liquidity risk exists when particular investments are impossible or difficult to sell. Although most of the fund’s investments must be liquid at the time of investment, investments may become illiquid after purchase by the fund, particularly during periods of market turmoil. Markets may become illiquid when, for instance, there are few, if any, interested buyers or sellers or when dealers are unwilling or unable to make a market for certain securities. When the fund holds illiquid investments, the portfolio may be harder to value, especially in changing markets, and if the fund is forced to sell these investments to meet redemption requests or for other cash needs, the fund may suffer a loss. In addition, when there is illiquidity in the market for certain investments, the fund, due to limitations on illiquid investments, may be unable to achieve its desired level of exposure to a certain sector.

More on the fund’s investment strategies, investments and risks cont’d

Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if a fee limitation is changed or terminated or if average net assets decrease. Net assets are more likely to decrease and fund expense ratios are more likely to increase when markets are volatile.

Tax risk. There is no guarantee that the income on the fund’s municipal securities will remain exempt from regular federal income tax. Unfavorable legislation, adverse interpretations by federal or state authorities, litigation or noncompliant conduct by the issuer of a municipal security could affect the tax-exempt status of municipal securities.

Prepayment or call risk. Many fixed income securities give the issuer the option to repay or call the security prior to its maturity date. Issuers often exercise this right when interest rates fall. Accordingly, if the fund holds a fixed income security subject to prepayment or call risk, it will not benefit fully from the increase in value that other fixed income securities generally experience when interest rates fall. Upon prepayment of the security, the fund would also be forced to reinvest the proceeds at then current yields, which would be lower than the yield of the security that was paid off. In addition, if the fund purchases a fixed income security at a premium (at a price that exceeds its stated par or principal value), the fund may lose the amount of the premium paid in the event of prepayment.

Extension risk. When interest rates rise, repayments of fixed income securities, particularly asset- and mortgage-backed securities, may occur more slowly than anticipated, extending the effective duration of these fixed income securities at below market interest rates and causing their market prices to decline more than they would have declined due to the rise in interest rates alone. This may cause the fund’s share price to be more volatile.

Risk of investing in fewer issuers. To the extent the fund invests its assets in a small number of issuers, the fund will be more susceptible to negative events affecting those issuers.

Risks relating to investments in municipal securities. Issuers of municipal securities tend to derive a significant portion of their revenue from taxes, particularly property and income taxes, and decreases in personal income levels and property values and other unfavorable economic factors, such as a general economic recession, adversely affect municipal securities. Municipal issuers may also be adversely affected by rising health care costs, increasing unfunded pension liabilities and by the phasing out of federal programs providing financial support. Where municipal securities are issued to finance particular projects, such as those relating to education, health care, transportation, and utilities, issuers often depend on revenues from those projects to make principal and interest payments. Adverse conditions and developments in those sectors can result in lower revenues to issuers of municipal securities and can also have an adverse effect on the broader municipal securities market.

There may be less public information available on municipal issuers or projects than other issuers, and valuing municipal securities may be more difficult. In addition, the secondary market for municipal securities is less well developed and liquid than other markets, and dealers may be less willing to offer and sell municipal securities in times of market turbulence. Changes in the financial condition of one or more individual municipal issuers (or one or more insurers of municipal issuers), or one or more defaults by municipal issuers or insurers, can adversely affect liquidity and valuations in the overall market for municipal securities. The value of municipal securities can also be adversely affected by regulatory and political developments affecting the ability of municipal issuers to pay interest or repay principal, actual or anticipated tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. In recent periods an increasing number of municipal issuers have defaulted on obligations, been downgraded or commenced insolvency proceedings. Financial difficulties of municipal issuers may continue or get worse.

Valuation risk. Many factors may influence the price at which the fund could sell any particular portfolio investment. The sales price may well differ—higher or lower—from the fund’s last valuation, and such differences could be significant, particularly for illiquid securities and securities that trade in relatively thin markets and/or markets that experience extreme volatility. If market conditions make it difficult to value some investments, the fund may value these investments using more subjective methods, such as fair value methodologies. Investors who purchase or redeem fund shares on days when the fund is holding fair-valued securities may receive fewer or more shares, or lower or higher redemption proceeds, than they would have received if the fund had not fair-valued the security or had used a different valuation methodology. The value of foreign securities, certain fixed income securities and currencies, as applicable, may be materially affected by events after the close of the markets on which they are traded, but before the fund determines its net asset value.

Cash management and defensive investing risk. The value of the investments held by the fund for cash management or defensive investing purposes can fluctuate. Like other fixed income securities, they are subject to risk, including market, interest rate and credit risk. If the fund holds cash uninvested, it will be subject to the credit risk of the depository institution holding the cash. If the fund holds cash uninvested, the fund will not earn income on the cash and the fund’s yield will go down. If a significant amount of the fund’s assets are used for cash management or defensive investing purposes, it may not achieve its investment objective.

Portfolio selection risk. The value of your investment may decrease if the subadviser’s judgment about the quality, relative yield, value or market trends affecting a particular security, industry, sector or region, or about interest rates is incorrect.

Not a money market fund. The fund is not a money market fund and is not subject to the strict rules that govern the quality, maturity, liquidity and other features of securities that money market funds may purchase. Under normal conditions, the fund’s investment may be more susceptible than a money market fund to interest rate risk, valuation risk, credit risk and other risks relevant to the fund’s investments. The fund does not attempt to maintain a stable net asset value. Therefore, the fund’s net asset value per share will fluctuate.

Please note that there are other factors that could adversely affect your investment and that could prevent the fund from achieving its investment objective. More information about risks appears in the SAI. Before investing, you should carefully consider the risks that you will assume.

Portfolio holdings

A description of the fund’s policies and procedures with respect to the disclosure of its portfolio holdings is available in the SAI. The fund posts its complete portfolio holdings at http://www.leggmason.com/individualinvestors/prospectuses (click on the name of the fund) on a quarterly basis. The fund intends to post its complete portfolio holdings 14 calendar days following the quarter-end. The fund intends to post partial information concerning the fund’s portfolio holdings (such as top 10 holdings or sector breakdowns, for example) on the Legg Mason funds’ website on a monthly basis. The fund intends to post this partial information 10 business days following each month-end. Such information will remain available until the next month’s or quarter’s holdings are posted.

More on fu nd management

Legg Mason Partners Fund Advisor, LLC (“LMPFA”) is the fund’s investment manager. LMPFA, with offices at 620 Eighth Avenue, New York, New York 10018, also serves as the investment manager of other Legg Mason-sponsored funds. LMPFA provides administrative and certain oversight services to the fund. LMPFA was formed in April 2006 as a result of an internal reorganization to consolidate advisory services after Legg Mason, Inc. (“Legg Mason”) acquired substantially all of Citigroup’s asset management business in December 2005. As of December 31, 2013, LMPFA’s total assets under management were approximately $225.4 billion.

Western Asset Management Company (“Western Asset”) provides the day-to-day portfolio management of the fund as subadviser. Western Asset, established in 1971, has offices at 385 East Colorado Boulevard, Pasadena, California 91101 and 620 Eighth Avenue, New York, New York 10018. Western Asset acts as investment adviser to institutional accounts, such as corporate pension plans, mutual funds and endowment funds. As of December 31, 2013, the total assets under management of Western Asset and its supervised affiliates were approximately $451.6 billion.

LMPFA pays the subadviser a portion of the management fee that it receives from the fund. The fund does not pay any additional advisory or other fees for advisory services provided by Western Asset.

LMPFA and Western Asset are wholly-owned subsidiaries of Legg Mason. Legg Mason, whose principal executive offices are at 100 International Drive, Baltimore, Maryland 21202, is a global asset management company. As of December 31, 2013, Legg Mason’s asset management operations, including Western Asset and its supervised affiliates, had aggregate assets under management of approximately $679.5 billion.

Investment professionals

The fund is managed by a broad team of investment professionals. The particular mix of investment professionals involved in developing and implementing investment strategies for the fund depends on the asset classes in which the fund invests. Senior members of the portfolio management team are responsible for the development of investment strategy and oversight for the fund and coordination of other relevant investment team members. They work together with the broader Western Asset investment management team on portfolio structure, duration weighting and term structure decisions.

The individuals responsible for day-to-day portfolio management, development of investment strategy, oversight and coordination of the fund are Stephen A. Walsh, Robert E. Amodeo, David T. Fare and Dennis J. McNamara. Mr. Fare has been a part of the portfolio management team for the fund since the fund’s inception. Messrs. Walsh and Amodeo have been a part of the portfolio management team for the fund since 2007. Mr. McNamara has been a part of the portfolio management team for the fund since 2012. Messrs. Fare, Walsh, Amodeo and McNamara have been employed by Western Asset as investment professionals for more than five years. It is anticipated that Mr. Walsh will step down as a member of the fund’s portfolio management team effective on or about March 31, 2014 and that S. Kenneth Leech will join the fund’s portfolio management team at that time. Mr. Leech has been employed by Western Asset as an investment professional for more than 20 years.

The SAI provides information about the investment professionals’ compensation, other accounts managed by the investment professionals and any fund shares held by the investment professionals.

Management fee

The fund pays a management fee at an annual rate of 0.45% of its average daily net assets.

For the fiscal year ended October 31, 2013, the fund paid LMPFA an effective management fee of 0.45% of the fund’s average daily net assets for management services.

A discussion regarding the basis for the Board’s approval of the fund’s management agreement and subadvisory agreement is available in the fund’s Semi-Annual Report for the period ended April 30, 2013.

Expense limitation

The manager has agreed to waive fees and/or reimburse operating expenses (other than interest, brokerage, taxes, extraordinary expenses and acquired fund fees and expenses) so that total annual operating expenses are not expected to exceed 0.75% for Class A shares, 1.10% for Class C shares, 0.85% for Class FI shares and 0.60% for Class I shares, subject to recapture as described below. These arrangements are expected to continue until December 31, 2015, may be terminated prior to that date by agreement of the manager and the Board, and may be terminated at any time after that date by the manager. These arrangements, however, may be modified by the manager to decrease total annual operating expenses at any time. The manager is also permitted to recapture amounts waived and/or reimbursed to a class during the same fiscal year if the class’ total annual operating expenses have fallen to a level below the limits described above. In no case will the manager recapture any amount that would result, on any particular business day of the fund, in the class’ total annual operating expenses exceeding the applicable limits described above or any other lower limit then in effect.

Distribution

LMIS, a wholly-owned broker/dealer subsidiary of Legg Mason, serves as the fund’s sole and exclusive distributor.

The fund has adopted a Rule 12b-1 shareholder services and distribution plan. Under the plan, the fund pays distribution and/or service fees, based on annualized percentages of average daily net assets, of up to 0.15% for Class A shares; up to 0.50% for Class C shares; and up to 0.25% for Class FI shares. These fees are an ongoing expense and, over time, will increase the cost of your investment and may cost you more than other types of sales charges. Class I shares are not subject to distribution and/or service fees under the plan.

Additional payments

In addition to distribution and service fees and sales charges, the distributor, the manager and/or their affiliates make payments for distribution, shareholder servicing, marketing and promotional activities and related expenses out of their profits and other available sources, including profits from their relationships with the fund. These payments are not reflected as additional expenses in the fee table contained in this Prospectus. The recipients of these payments may include the fund’s distributor and affiliates of the manager, as well as non-affiliated broker/dealers, insurance companies, financial institutions and other financial intermediaries through which investors may purchase shares of the fund, including your financial intermediary. The total amount of these payments is substantial, may be substantial to any given recipient and may exceed the costs and expenses incurred by the recipient for any fund-related marketing or shareholder servicing activities. The payments described in this paragraph are often referred to as “revenue sharing payments.” Revenue sharing arrangements are separately negotiated between the distributor, the manager and/or their affiliates, and the recipients of these payments.

Revenue sharing payments create an incentive for an intermediary or its employees or associated persons to recommend or sell shares of the fund to you. Contact your financial intermediary for details about revenue sharing payments it receives or may receive. Revenue sharing payments, as well as payments under the shareholder services and distribution plan (where applicable), also benefit the manager, the distributor and their affiliates to the extent the payments result in more assets being invested in the fund on which fees are being charged.

Choosing a class of shares to buy

Individual investors can generally invest in Class A and Class C shares. Individual investors who invest directly with the fund and who meet the $1,000,000 minimum initial investment requirement may purchase Class I shares. In addition, participants in Eligible Investment Programs may exchange Class A and Class C shares for Class I shares of the fund under certain limited circumstances.

Institutional Investors and Clients of Eligible Financial Intermediaries should refer to “Institutional Investors — eligible investors” below for a description of the classes available to them. Each class has different sales charges and expenses, allowing you to choose a class that may be appropriate for you.

When choosing which class of shares to buy, you should consider:

When choosing between Class A and Class C shares, keep in mind that, generally speaking, the larger the size of your investment and the longer your investment horizon, the more likely it will be that Class C shares will not be as advantageous as Class A shares. The annual distribution and/or service fees on Class C shares may cost you more over the longer term than the front-end sales charge and service fees you would have paid for larger purchases of Class A shares. If you are eligible to purchase Class I shares, you should be aware that Class I shares are not subject to a front-end sales charge and generally have lower annual expenses than Class A or Class C shares.

Each class of shares is authorized to pay fees for recordkeeping services to Service Agents. As a result, operating expenses of classes that incur new or additional recordkeeping fees may increase over time.

You may buy shares:

Your Service Agent may provide shareholder services that differ from the services provided by other Service Agents. Services provided by your Service Agent may vary by class. You should ask your Service Agent to explain the shareholder services it provides for each class and the compensation it receives in connection with each class. Remember that your Service Agent may receive different compensation depending on the share class in which you invest.

Your Service Agent may not offer all classes of shares. You should contact your Service Agent for further information.

More information about the fund’s classes of shares is available through the Legg Mason funds’ website. You’ll find detailed information about sales charges and ways you can qualify for reduced or waived sales charges, including:

To visit the website, go to http://www.leggmason.com/individualinvestors/products, and click on the name of the fund in the dropdown menu.

Comparing the fund’s classes

The following table compares key features of the fund’s classes. You should review the fee table and example at the front of this Prospectus carefully before choosing your share class. Your Service Agent can help you choose a class that may be appropriate for you. Please contact your Service Agent regarding the availability of Class FI shares. You may be required to provide appropriate documentation confirming your eligibility to invest in this share class. Your Service Agent may receive different compensation depending upon which class you choose.

Sales char ges

Class A shares

You buy Class A shares at the offering price, which is the net asset value plus a sales charge. You pay a lower rate as the size of your investment increases to certain levels called breakpoints. You do not pay a sales charge on the fund’s distributions or dividends that you reinvest in additional Class A shares.

The table below shows the rate of sales charge you pay, depending on the amount you purchase. It also shows the amount of broker/dealer compensation that will be paid out of the sales charge if you buy shares from a Service Agent. For Class A shares sold by the distributor, the distributor will receive the sales charge imposed on purchases of Class A shares (or any contingent deferred sales charge paid on redemptions) and will retain the full amount of such sales charge. Service Agents will receive a distribution and/or service fee payable on Class A shares at an annual rate of up to 0.15% of the average daily net assets represented by the Class A shares serviced by them.

Investments of $500,000 or more

You do not pay an initial sales charge when you buy $500,000 or more of Class A shares. However, if you redeem these Class A shares within 18 months of purchase, you will pay a contingent deferred sales charge of 0.50%.

Qualifying for a reduced Class A sales charge

There are several ways you can combine multiple purchases of shares of funds sold by the distributor to take advantage of the breakpoints in the Class A sales charge schedule. In order to take advantage of reductions in sales charges that may be available to you when you purchase fund shares, you must inform your Service Agent or the fund if you are eligible for a letter of intent or a right of accumulation and if you own shares of other funds that are eligible to be aggregated with your purchases. Certain records, such as account statements, may be necessary in order to verify your eligibility for a reduced sales charge.

with the dollar amount of your next purchase of Class A shares for purposes of calculating the initial sales charges.

If you hold fund shares in accounts at two or more Service Agents, please contact your Service Agents to determine which shares may be combined.

Shares of money market funds sold by the distributor acquired by exchange from other funds offered with a sales charge may be combined. Shares of money market funds sold by the distributor that were not acquired by exchange from other funds offered with a sales charge may not be combined. Please contact your Service Agent or the fund for additional information.

Certain trustees and other fiduciaries may be entitled to combine accounts in determining their sales charge.

are eligible for inclusion under the letter of intent, based on the public offering price at the time of the purchase and any capital appreciation on those shares. In addition, you can include the current value of any eligible holdings toward your asset goal amount.

If you hold shares of funds sold by the distributor in accounts at two or more Service Agents, please contact your Service Agents to determine which shares may be credited toward your asset goal amount.

Shares of money market funds sold by the distributor acquired by exchange from other funds offered with a sales charge may be credited toward your asset goal amount. Please contact your Service Agent for additional information.

If you do not meet your asset goal amount, shares in the amount of any sales charges due, based on the amount of your actual purchases, will be redeemed from your account.

Waivers for certain Class A investors

Class A initial sales charges are waived for certain types of investors, including:

If you qualify for a waiver of the Class A initial sales charge, you must notify your Service Agent or the fund at 1-877-721-1926 at the time of purchase and provide sufficient information at the time of purchase to permit verification that the purchase qualifies for the initial sales charge waiver.

If you want to learn about additional waivers of Class A initial sales charges, contact your Service Agent, consult the SAI or visit the Legg Mason funds’ website, http://www.leggmason.com/individualinvestors/products, and click on the name of the fund in the dropdown menu.

Class C shares

You buy Class C shares at net asset value with no initial sales charge and no contingent deferred sales charge. However, if you exchange Class C shares that were not subject to a contingent deferred sales charge when initially purchased for Class C shares of a fund that imposes a contingent deferred sales charge, your contingent deferred sales charge will be measured from the date of your exchange.

Service Agents receive an annual distribution and/or service fee of up to 0.50% of the average daily net assets represented by the Class C shares serviced by them.

Class FI shares

You buy Class FI shares at net asset value with no initial sales charge and no contingent deferred sales charge when redeemed.

Service Agents receive an annual distribution and/or service fee of up to 0.25% of the average daily net assets represented by the Class FI shares serviced by them.

Class I shares

You buy Class I shares at net asset value with no initial sales charge and no contingent deferred sales charge when redeemed. Class I shares are not subject to any distribution and/or service fees.

More abo ut contingent deferred sales charges

The contingent deferred sales charge is based on the net asset value at the time of purchase or redemption, whichever is less, and therefore you do not pay a sales charge on amounts representing appreciation or depreciation.

In addition, you do not pay a contingent deferred sales charge:

Each time you place a request to redeem shares, the fund will first redeem any shares in your account that are not subject to a contingent deferred sales charge and then redeem the shares in your account that have been held the longest.

If you redeem shares of a fund sold by the distributor and pay a contingent deferred sales charge, you may, under certain circumstances, reinvest all or part of the redemption proceeds within 60 days and receive pro rata credit for any contingent deferred sales charge imposed on the prior redemption. Please contact your Service Agent for additional information.

The distributor receives contingent deferred sales charges as partial compensation for its expenses in selling shares, including the payment of compensation to your Service Agent.

Contingent deferred sales charge waivers

The contingent deferred sales charge for each share class will generally be waived:

If you want to learn more about additional waivers of contingent deferred sales charges, contact your Service Agent, consult the SAI or visit the Legg Mason funds’ website, http://www.leggmason.com/individualinvestors/products, and click on the name of the fund in the dropdown menu.

Institutional Inve stors — eligible investors

Clients of Eligible Financial Intermediaries

“Clients of Eligible Financial Intermediaries” are investors who invest in the fund through financial intermediaries that (i) charge such investors an ongoing fee for advisory, investment, consulting or similar services, or (ii) have entered into an agreement with the distributor to offer Class A, Class FI or Class I shares through a no-load network or platform (“Eligible Investment Programs”). Such investors may include pension and profit sharing plans, other employee benefit trusts, endowments, foundations and corporations. Eligible Investment Programs may also include college savings vehicles such as Section 529 plans and direct retail investment platforms through mutual fund “supermarkets,” where the sponsor links its client’s account to a master account in the sponsor’s name. The financial intermediary may impose separate investment minimums.

Clients of Eligible Financial Intermediaries may generally invest in Class A, Class FI and Class I shares. Class I shares are available for exchange from Class A or Class C shares of the fund held by participants in Eligible Investment Programs under certain limited circumstances.

Institutional Investors

“Institutional Investors” may include corporations, banks, trust companies, insurance companies, investment companies, foundations, endowments, defined benefit plans and other similar entities. The distributor or the financial intermediary may impose additional eligibility requirements or criteria to determine if an investor, including the types of investors listed above, qualifies as an Institutional Investor.

Institutional Investors may invest in Class I shares if they meet the $1,000,000 minimum initial investment requirement. Institutional Investors may also invest in Class A and Class C shares, which have different investment minimums, fees and expenses.

Class FI shares

Class FI shares are offered only to Clients of Eligible Financial Intermediaries.

Class I shares

Class I shares are offered only to Institutional Investors and individual investors (investing directly with the fund) who meet the $1,000,000 minimum initial investment requirement, Clients of Eligible Financial Intermediaries and other investors authorized by LMIS. Certain waivers of these requirements for individuals associated with the fund, Legg Mason or its affiliates are discussed in the SAI.

Other considerations

Financial intermediaries may choose to impose qualification requirements that differ from the fund’s share class eligibility standards. In certain cases this could result in the selection of a share class with higher distribution and/or service fees than otherwise would have been charged. The fund is not responsible for, and has no control over, the decision of any financial intermediary to impose such differing requirements. Please consult with your financial intermediary for more information about available share classes.

Your Service Agent may not offer all share classes. Please contact your Service Agent for additional details.

Exchangi ng shares

Other thin gs to know about transactions

When you buy, exchange or redeem shares, your request must be in good order. This means you have provided the following information, without which your request may not be processed:

The fund generally will not permit non-resident aliens with non-U.S. addresses to establish accounts. U.S. citizens with APO/FPO addresses or addresses in the United States (including its territories) and resident aliens with U.S. addresses are permitted to establish accounts with the fund. Subject to the requirements of local law, U.S. citizens residing in foreign countries are permitted to establish accounts with the fund.

In certain circumstances, such as during periods of market volatility, severe weather and emergencies, shareholders may experience difficulties placing exchange or redemption orders by telephone. In that case, shareholders should consider using the fund’s other exchange and redemption procedures described under “Exchanging shares” and “Redeeming shares.”

The transfer agent or the fund will employ reasonable procedures to confirm that any telephone exchange or redemption request is genuine, which may include recording calls, asking the caller to provide certain personal identification information, sending you a written confirmation or requiring other confirmation procedures from time to time. If these procedures are followed, neither the fund nor its agents will bear any liability for these transactions.

The fund has the right to:

For your protection, the fund or your Service Agent may request additional information in connection with large redemptions, unusual activity in your account, or otherwise to ensure your redemption request is in good order. Please contact your Service Agent or the fund for more information.

Signature guarantees

To be in good order, your redemption request must include a signature guarantee if you:

You can obtain a signature guarantee from most banks, dealers, brokers, credit unions and federal savings and loan institutions, but not from a notary public.

Anti-money laundering

Federal anti-money laundering regulations require all financial institutions to obtain, verify and record information that identifies each person who opens an account. When you sign your account application, you may be asked to provide additional information in order for the fund to verify your identity in accordance with these regulations. Accounts may be restricted and/or closed, and the monies withheld, pending verification of this information or as otherwise required under these and other federal regulations.

Other things to know about transactions cont’d

Small account fees/Mandatory redemptions

Small accounts may be subject to a small account fee or to mandatory redemption, as described below, depending on whether the account is held directly with the fund or through a Service Agent.

Direct accounts

Direct accounts generally include accounts held in the name of the individual investor on the fund’s books and records. To offset the relatively higher impact on fund expenses of servicing smaller direct accounts, if your shares are held in a direct account and the value of your account is below $1,000 (if applicable, $250 for retirement plans that are not employer-sponsored) for any reason (including declines in net asset value), the fund may charge you a fee of $3.75 per account that is determined and assessed quarterly on the last business day of the quarter (with an annual maximum of $15.00 per account). The small account fee will be charged by redeeming shares in your account. If the value of your account is $3.75 or less, the amount in the account may be exhausted to pay the small account fee. The small account fee will not be assessed on systematic investment plans until the end of the first quarter after the account has been established for 15 months. Payment of the small account fee through a redemption of fund shares may result in tax consequences to you (see “Taxes” for more information).

The small account fee will not be charged on, if applicable: (i) Retirement Plans (but will be charged on other plans that are not employer-sponsored such as traditional and Roth individual retirement accounts, Coverdell education savings accounts, individual 403(b)(7) custodial accounts, Keogh plans, SEPs, SARSEPs, SIMPLE IRAs or similar accounts); (ii) Legg Mason funds that have been closed to subsequent purchases for all classes; (iii) accounts that do not have a valid address as evidenced by mail being returned to the fund or its agents; and (iv) Class FI and Class I shares.

If your share class is no longer offered, you may not be able to bring your account up to the minimum investment amount (although you may exchange into existing accounts of other Legg Mason funds in which you hold the same share class, to the extent otherwise permitted by those funds and subject to any applicable sales charges).

Some shareholders who hold accounts in Classes A and B of the same fund may have those accounts aggregated for the purposes of these calculations. Please contact the fund or your Service Agent for more information.

Non-direct accounts

“Non-direct accounts” include omnibus accounts and accounts jointly maintained by the Service Agent and the fund. Such accounts are not subject to the small account fee that may be charged to direct accounts.

The fund reserves the right to ask you to bring your non-direct account up to a minimum investment amount determined by your Service Agent if the aggregate value of the fund shares in your account is less than $500 for any reason (including solely due to declines in net asset value and/or failure to invest at least $500 within a reasonable period). You will be notified in writing and will have 60 days to make an additional investment to bring your account value up to the required level. If you choose not to do so within this 60-day period, the fund may close your account and send you the redemption proceeds. If your share class is no longer offered, you may not be able to bring your account up to the minimum investment amount. Some shareholders who hold accounts in multiple classes of the same fund may have those accounts aggregated for the purposes of these calculations. If your account is closed, you will not be eligible to have your account reinstated without imposition of any sales charges that may apply to your new purchase.

Please contact your Service Agent for more information. Any redemption of fund shares may result in tax consequences to you (see “Taxes” for more information).

All accounts

The fund may, with prior notice, change the minimum size of accounts subject to mandatory redemption, which may vary by class, implement fees for small non-direct accounts or change the amount of the fee for small direct accounts.

Subject to applicable law, the fund may, with prior notice, adopt other policies from time to time requiring mandatory redemption of shares in certain circumstances.

For more information, please contact your Service Agent or the fund or consult the SAI.

Frequent trading of fund shares

Frequent purchases and redemptions of fund shares (also known as short-term trading or frequent trading) may, in many cases, interfere with the efficient management of the fund, increase fund transaction costs, and have a negative effect on the fund’s long-term shareholders. For example, in order to handle large flows of cash into and out of the fund, the subadviser may need to allocate more assets to cash or other short-term investments or sell securities, rather than maintaining full investment in securities selected to achieve the fund’s investment objective. Frequent trading may cause the fund to sell securities at less favorable prices. Transaction costs, such as brokerage commissions and market spreads, can detract from the fund’s performance. In addition, the return received by long-term shareholders may be reduced when trades by other shareholders are made in an

effort to take advantage of certain pricing discrepancies, when, for example, it is believed that the fund’s share price, which is determined at the close of the NYSE on each trading day, does not accurately reflect the value of the fund’s investments. Funds investing in foreign securities have been particularly susceptible to this form of arbitrage, but other funds could also be affected.

Some investors are seeking higher yields for their short term investments by investing in shorter term fixed income funds. The fund is often used for short term investments and permits short term trading of fund shares. This short term trading may result in additional costs to the fund.

The fund does not anticipate that frequent purchases and redemptions, under normal circumstances, will have significant adverse consequences to the fund or its shareholders. The fund’s manager and subadviser believe that, because the fund’s portfolio will normally include a significant percentage of short-term investments, it can accommodate more frequent purchases and redemptions than longer-term fixed income funds. On this basis, the Board has determined that it is appropriate for the fund not to have a policy to discourage frequent trading of fund shares. The fund reserves the right to implement frequent trading policies or other restrictions in the future. The fund also reserves the right to refuse any client or reject any purchase order for shares (including exchanges) for any reason.

Record ownership

If you hold shares through a Service Agent, your Service Agent may establish and maintain your account and be the shareholder of record. In the event that the fund holds a shareholder meeting, your Service Agent, as record holder, will be entitled to vote your shares and may seek voting instructions from you. If you do not give your Service Agent voting instructions, your Service Agent, under certain circumstances, may nonetheless be entitled to vote your shares.

Dividends , other distributions and taxes

Dividends and other distributions

The fund declares dividends from any net investment income daily and pays them monthly. Shares will begin to earn dividends on the settlement date of purchase. The fund generally distributes capital gain, if any, once a year, typically in December. The fund may pay additional distributions and dividends in order to avoid a federal tax.

Unless you elect to receive dividends and/or other distributions in cash, your dividends and capital gain distributions will be automatically reinvested in shares of the same class you hold, at the net asset value determined on the reinvestment date. You do not pay a sales charge on reinvested distributions or dividends.

If you hold Class A or Class C shares directly with the fund, you may instruct the fund to have your dividends and/or distributions invested in the corresponding class of shares of another fund sold by the distributor, subject to the following conditions:

To change those instructions, you must notify your Service Agent or the fund at least three days before the next distribution is to be paid.

Please contact your Service Agent or the fund to discuss what options are available to you for receiving your dividends and other distributions.

The Board reserves the right to revise the dividend policy or postpone the payment of dividends if warranted in the Board’s judgment due to unusual circumstances.

Taxes

The following discussion is very general, applies only to shareholders who are U.S. persons, and does not address shareholders subject to special rules, such as those who hold fund shares through an IRA, 401(k) plan or other tax-advantaged account. Except as specifically noted, the discussion is limited to federal income tax matters, and does not address state, local, foreign or non-income taxes. Further information regarding taxes, including certain federal income tax considerations relevant to non-U.S. persons, is included in the SAI. Because each shareholder’s circumstances are different and special tax rules may apply, you should consult your tax adviser about federal, state, local and/or foreign tax considerations that may be relevant to your particular situation.

You may receive three different types of distributions from the fund: exempt-interest dividends, ordinary dividends and capital gain dividends. Most distributions are expected to be exempt-interest dividends, which are exempt from federal income tax but may be subject to state or local income taxes. In general, redeeming shares, exchanging shares and receiving distributions other than exempt-interest dividends (whether in cash, additional shares or shares of another fund) are all taxable events. An exchange between classes of shares of the same fund normally is not taxable for federal income tax purposes, whether or not the shares are held in a taxable account.

The following table summarizes the tax status of certain transactions related to the fund.

Distributions attributable to short-term capital gains are taxable to you as ordinary income. The fund does not expect any distributions to be treated as qualified dividend income, which for noncorporate shareholders may be taxable at reduced rates. Some exempt-interest dividends may be subject to the federal alternative minimum tax. Distributions of net capital gain reported by the fund as capital gain dividends are taxable to you as long-term capital gain regardless of how long you have owned your shares. Noncorporate shareholders ordinarily pay tax at reduced rates on long-term capital gain.

You may want to avoid buying shares when the fund is about to declare a capital gain distribution because it will be taxable to you even though it may economically represent a return of a portion of your investment.

A Medicare contribution tax is imposed at the rate of 3.8% on net investment income of U.S. individuals with income exceeding specified thresholds, and on undistributed net investment income of certain estates and trusts. Net investment income generally includes for this purpose dividends (other than exempt-interest dividends) and capital gain distributions paid by the fund and gain on the redemption or exchange of fund shares.

A dividend declared by the fund in October, November or December and paid during January of the following year will, in certain circumstances, be treated as paid in December for tax purposes.

After the end of each year, your Service Agent or the fund will provide you with information about the distributions and dividends you received, including exempt-interest dividends, and any redemptions of shares during the previous year. Because each shareholder’s circumstances are different and special tax rules may apply, you should consult your tax adviser about your investment in the fund.

Share pri ce

You may buy, exchange or redeem shares at their net asset value next determined after receipt of your request in good order, adjusted for any applicable sales charge. The fund’s net asset value per share is the value of its assets minus its liabilities divided by the number of shares outstanding. Net asset value is calculated separately for each class of shares.

The fund calculates its net asset value every day the NYSE is open. The fund generally values its securities and other assets and calculates its net asset value as of the close of regular trading on the NYSE, normally at 4:00 p.m. (Eastern time). If the NYSE closes at another time, the fund will calculate its net asset value as of the actual closing time. The NYSE is closed on certain holidays listed in the SAI.

In order to buy, redeem or exchange shares at a certain day’s price, you must place your order with your Service Agent or the transfer agent before the NYSE closes on that day. If the NYSE closes early on that day, you must place your order prior to the actual closing time. It is the responsibility of the Service Agent to transmit all orders to buy, exchange or redeem shares to the transfer agent on a timely basis.

Valuation of the fund’s securities and other assets is performed in accordance with procedures approved by the Board. These procedures delegate most valuation functions to the manager, which generally uses independent third party pricing services approved by the fund’s Board. Under the procedures, assets are valued as follows:

Many factors may influence the price at which the fund could sell any particular portfolio investment. The sales price may well differ—higher or lower—from the fund’s last valuation, and such differences could be significant, particularly for securities that trade in relatively thin markets and/or markets that experience extreme volatility. Moreover, valuing securities using fair value methodologies involves greater reliance on judgment than valuing securities based on market quotations. A fund that uses fair value methodologies may value those securities higher or lower than another fund using market quotations or its own fair value methodologies to price the same securities. There can be no assurance that the fund could obtain the value assigned to a security if it were to sell the security at approximately the time at which the fund determines its net asset value. Investors who purchase or redeem fund shares on days when the fund is holding fair-valued securities may receive a greater or lesser number of shares, or higher or lower redemption proceeds, than they would have received if the fund had not fair-valued the security or had used a different methodology.

Financial highlights

The financial highlights tables are intended to help you understand the performance of each class for the past five years, unless otherwise noted. No financial highlights are presented for Class FI shares because no Class FI shares were outstanding for the periods shown. The returns for Class FI shares will differ from those of the other classes to the extent their expenses differ. Certain information reflects financial results for a single share. Total return represents the rate that a shareholder would have earned (or lost) on a fund share assuming reinvestment of all dividends and distributions. The information in the following tables has been derived from the fund’s financial statements, which have been audited by KPMG LLP, independent registered public accounting firm, whose report, along with the fund’s financial statements, is included in the annual report (available upon request).

Legg Mason Funds Privacy and Security Notice

Your Privacy and the Security of Your Personal Information is Very Important to the Legg Mason Funds

This Privacy and Security Notice (the “Privacy Notice”) addresses the Legg Mason Funds’ privacy and data protection practices with respect to nonpublic personal information the Funds receive. The Legg Mason Funds include any funds sold by the Funds’ distributor, Legg Mason Investor Services, LLC, as well as Legg Mason-sponsored closed-end funds and certain closed-end funds managed or sub-advised by Legg Mason or its affiliates. The provisions of this Privacy Notice apply to your information both while you are a shareholder and after you are no longer invested with the Funds.

The Type of Nonpublic Personal Information the Funds Collect About You

The Funds collect and maintain nonpublic personal information about you in connection with your shareholder account. Such information may include, but is not limited to:

How the Funds Use Nonpublic Personal Information About You

The Funds do not sell or share your nonpublic personal information with third parties or with affiliates for their marketing purposes, or with other financial institutions or affiliates for joint marketing purposes, unless you have authorized the Funds to do so. The Funds do not disclose any nonpublic personal information about you except as may be required to perform transactions or services you have authorized or as permitted or required by law. The Funds may disclose information about you to:

Except as otherwise permitted by applicable law, companies acting on the Funds’ behalf are contractually obligated to keep nonpublic personal information the Funds provide to them confidential and to use the information the Funds share only to provide the services the Funds ask them to perform.

The Funds may disclose nonpublic personal information about you when necessary to enforce their rights or protect against fraud, or as permitted or required by applicable law, such as in connection with a law enforcement or regulatory request, subpoena, or similar legal process. In the event of a corporate action or in the event a Fund service provider changes, the Funds may be required to disclose your nonpublic personal information to third parties. While it is the Funds’ practice to obtain protections for disclosed information in these types of transactions, the Funds cannot guarantee their privacy policy will remain unchanged.

Keeping You Informed of the Funds’ Privacy and Security Practices

The Funds will notify you annually of their privacy policy as required by federal law. While the Funds reserve the right to modify this policy at any time they will notify you promptly if this privacy policy changes.

The Funds’ Security Practices

The Funds maintain appropriate physical, electronic and procedural safeguards designed to guard your nonpublic personal information. The Funds’ internal data security policies restrict access to your nonpublic personal information to authorized employees, who may use your nonpublic personal information for Fund business purposes only.

Although the Funds strive to protect your nonpublic personal information, they cannot ensure or warrant the security of any information you provide or transmit to them, and you do so at your own risk. In the event of a breach of the confidentiality or security of your nonpublic personal information, the Funds will attempt to notify you as necessary so you can take appropriate protective steps. If you have consented to the Funds using electronic communications or electronic delivery of statements, they may notify you under such circumstances using the most current email address you have on record with them.

In order for the Funds to provide effective service to you, keeping your account information accurate is very important. If you believe that your account information is incomplete, not accurate or not current, or if you have questions about the Funds’ privacy practices, write the Funds using the contact information on your account statements, email the Funds by clicking on the Contact Us section of the Funds’ website at www.leggmason.com, or contact the Funds at 1-877-721-1926.

Western Asset

Short Duration Municipal Income Fund

You may visit the fund’s website, http://www.leggmason.com/individualinvestors/prospectuses, for a free copy of a Prospectus, Statement of Additional Information (“SAI”) or an Annual or Semi-Annual Report.

Shareholder reports Additional information about the fund’s investments is available in the fund’s Annual and Semi-Annual Reports to shareholders. In the fund’s Annual Report, you will find a discussion of the market conditions and investment strategies that significantly affected the fund’s performance during its last fiscal year. The independent registered public accounting firm’s report and financial statements in the fund’s Annual Report are incorporated by reference into (are legally a part of) this Prospectus.

The fund sends only one report to a household if more than one account has the same last name and same address. Contact your Service Agent or the fund if you do not want this policy to apply to you.

Statement of additional information The SAI provides more detailed information about the fund and is incorporated by reference into (is legally a part of) this Prospectus.

You can make inquiries about the fund or obtain shareholder reports or the SAI (without charge) by contacting your Service Agent, by calling the fund at 1-877-721-1926, or by writing to the fund at 100 First Stamford Place, Attn: Shareholder Services – 5 ^th Floor, Stamford, Connecticut 06902.

Information about the fund (including the SAI) can be reviewed and copied at the Securities and Exchange Commission’s (the “SEC”) Public Reference Room in Washington, D.C. Information on the operation of the Public Reference Room may be obtained by calling the SEC at 1-202-551-8090. Reports and other information about the fund are available on the EDGAR Database on the SEC’s Internet site at http://www.sec.gov . Copies of this information may be obtained for a duplicating fee by electronic request at the following E-mail address: publicinfo@sec.gov , or by writing the SEC’s Public Reference Room, Washington, D.C. 20549-1520.

If someone makes a statement about the fund that is not in this Prospectus, you should not rely upon that information. Neither the fund nor the distributor is offering to sell shares of the fund to any person to whom the fund may not lawfully sell its shares.

(Investment Company Act

file no. 811-04254)

FD02716ST 03/14

March 1, 2014

LEGG MASON PARTNERS INCOME TRUST

WESTERN ASSET SHORT DURATION MUNICIPAL INCOME FUND

Class A (SHDAX), Class C (SHDLX), Class FI and Class I (SMDYX)

620 Eighth Avenue

New York, New York 10018

1-877-721-1926