united states
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

SCHEDULE TO

TENDER OFFER STATEMENT UNDER SECTION 14(D)(1) OR 13(E)(1)
OF THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

MFS High Yield Municipal Trust
(Name of Subject Company (Issuer))

MFS High Yield Municipal Trust
(Name of Filing Person (Issuer))

Common Shares, Without Par
(Title of Class of Securities)

59318E102
(CUSIP Number of Class of Securities)

Christopher R. Bohane
Massachusetts Financial Services Company
111 Huntington Avenue
Boston, MA 02199
Telephone: (617) 954-5000

(Name, address and telephone number of person authorized to receive notices and communications on behalf of filing persons)

With a Copy to:

David C. Sullivan
Ropes & Gray LLP
Prudential Tower
800 Boylston Street
Boston, MA 02199-3600
Telephone: (617) 951-7000

Check the following box if the filing is a final amendment reporting the results of the tender offer. o

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

explanatory note

This Amendment No. 3 (“Amendment No. 3”) amends and supplements the Schedule TO filed with the U.S, Securities and Exchange Commission (the “SEC”) on March 04, 2026, as amended April 06, 2026, and May 6, 2026, regarding the communications made for the commencement of a tender offer (the “Offer”) on April 6, 2026 by MFS High Yield Municipal Trust, a closed-end management investment company (the “Fund”), to purchase for cash up to 50% or 12,746,391 shares of the Fund’s outstanding common shares (the “Shares”) upon the terms and subject to the conditions of the Offer.

This Amendment No. 3 to Schedule TO is intended to satisfy the requirements pursuant to Rule 13e-4(c)(3) of the Exchange Act.

Forward-Looking Statements

This document contains 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 the Fund’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; the Fund undertakes no obligation to update or review any forward-looking statements. You are urged to carefully consider all such factors.

Items 1 through 11 and Item 13

The information set forth in the Offer to Purchase and the related Letter of Transmittal is incorporated herein by reference into this Amendment No. 3 in answer to Item 1 through Item 11 and Item 13 of Schedule TO.

Items 12. EXHIBITS

Item 12 of the Schedule TO is hereby amended and supplemented to add the following exhibits:

SIGNATURE

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ATTACHMENTS / EXHIBITS

c116384_ex-a5v.htm

c116384_exs-ixbrl.htm

IDEA: R1.htm

IDEA: R2.htm

IDEA: R3.htm

IDEA: FilingSummary.xml

IDEA: MetaLinks.json

IDEA: c116384_exs-ixbrl_htm.xml