MFS^® High Yield Municipal Trust (NYSE:CMU) announced today that it will complete an optional partial redemption of its Remarketable Variable Rate MuniFund Term Preferred Shares, Series 2051 ("Series 2051 RVMTP Shares") on May 1, 2026 (the "Redemption Date").

On the Redemption Date, CMU will redeem up to 180 of the 510 Series 2051 RVMTP Shares at a redemption price equal to the liquidation preference of $100,000 per share plus unpaid dividends and other distributions accumulated from the original issue date to, but excluding, the Redemption Date. The redemption of a portion of CMU's Series 2051 RVMTP Shares will reduce the amount of its leverage attributable to preferred shares.

All regulatory requirements relating to the redemption of CMU's Series 2051 RVMTP Shares have been satisfied by MFS Investment Management. The Tender and Paying Agent is The Bank of New York Mellon and its address is: 101 Barclay Street, Floor 7E, New York, New York 10286. Payment of the redemption price for CMU's Series 2051 RVMTP Shares will be sent to the holder by the Tender and Paying Agent on the Redemption Date.

Cautionary Statement Regarding Forward-Looking Statements

This press release may contain statements regarding plans and expectations for the future that constitute forward-looking statements within The Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact are forward-looking and can be identified by the use of words such as "may," "will," "expect," "anticipate," "estimate," "believe," "continue," or other similar words. Such forward-looking statements are based on CMU's current plans and expectations, are not guarantees of future results or performance, and are subject to risks and uncertainties that could cause actual results to differ materially from those described in the forward-looking statements. All forward-looking statements are as of the date of this release only; CMU undertakes no obligation to update or review any forward-looking statements. You are urged to carefully consider all such factors.

About CMU

MFS^® High Yield Municipal Trust is a closed-end investment company product advised by MFS Investment Management. Closed-end funds, unlike open-end funds, are not continuously offered. There is a one-time public offering and once issued, common shares of a closed-end fund are bought and sold in the open market through a stock exchange. Shares may trade at a discount to the net asset value per share. Shares of CMU are not FDIC-insured and are not deposits or other obligations of, or guaranteed by, any bank. Shares of CMU involve investment risk, including possible loss of principal.

About MFS Investment Management^®

In 1924, MFS^® launched the first US open-end mutual fund, opening the door to the markets for millions of everyday investors. Today, as a full-service global investment manager serving financial advisors, intermediaries and institutional clients, MFS still serves a single purpose: to create long term value for clients by allocating capital responsibly. That takes our powerful investment approach combining collective expertise, thoughtful risk management and long-term discipline. Supported by our culture of shared values and collaboration, our teams of diverse thinkers actively debate ideas and assess material risks to uncover what we believe are the best investment opportunities in the market. As of February 28, 2026, MFS manages $669.8 billion in assets under management. Please visit mfs.com for more information.

MFS Investment Management

111 Huntington Ave., Boston, MA 02199

67975.1

View source version on businesswire.com: https://www.businesswire.com/news/home/20260401498713/en/

Dan Flaherty, +1 617.954.4256

MFS High Yield Municipal Trust Announces Optional Partial Redemption of Preferred Shares