[SCHEDULE 13D/A] MFS HIGH YIELD MUNICIPAL TRUST Amended Major Shareholder Report

Rhea-AI Filing Summary

MFS High Yield Municipal Trust (CMU) received an updated Schedule 13D/A from Bulldog Investors, LLP, Phillip Goldstein and Andrew Dakos reflecting their current ownership stakes. Based on 25,492,782 CMU shares outstanding as of 11/30/25, Phillip Goldstein is deemed to beneficially own 3,455,205 shares, or 13.55% of the common stock. Bulldog Investors, LLP is deemed to beneficially own 3,072,220 shares, or 12.05%, while Andrew Dakos is deemed to beneficially own 2,957,332 shares, or 11.60%. The filing notes that Bulldog has sole voting and dispositive power over 120,488 shares and shared power over 2,951,732 shares, with certain clients sharing this power. It also lists recent CMU trading activity over the last 60 days, including purchases and sales around the mid-$3.60 price range.

Insights

Closed-end fund activist & governance analyst

Goldstein/Dakos maintain double-digit CMU stakes, signaling ongoing activist-level involvement.

Bulldog Investors, Phillip Goldstein and Andrew Dakos report sizeable positions in CMU, each above 11% of outstanding shares. These levels typically reflect an ability to influence governance, voting outcomes and strategic direction at a closed-end fund.

The filing details sole versus shared voting and dispositive power, with Bulldog controlling 120,488 shares directly and sharing authority on 2,951,732 shares. Recent trades around $3.51–$3.65 show active position management rather than a static holding.

Future company communications and shareholder meetings will show how these stakes translate into voting behavior or proposals, since the amendment itself mainly updates ownership data and recent trading activity.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 10)

MFS High Yield Municipal Trust

(Name of Issuer)

Common Stock

(Title of Class of Securities)

59318E102

(CUSIP Number)

Phillip Goldstein
250 Pehle Ave., Suite 708
Saddle Brook, NJ, 07663
914 747-5262

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

04/07/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 59318E102

1

Name of reporting person

Bulldog Investors, LLP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 120,488.00
8	Shared Voting Power 2,951,732.00
9	Sole Dispositive Power 120,488.00
10	Shared Dispositive Power 2,951,732.00

11

Aggregate amount beneficially owned by each reporting person

3,072,220.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

12.05 %

14

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13D

CUSIP Number(s): 59318E102

1

Name of reporting person

Phillip Goldstein

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 120,488.00
8	Shared Voting Power 3,334,717.00
9	Sole Dispositive Power 120,488.00
10	Shared Dispositive Power 3,334,717.00

11

Aggregate amount beneficially owned by each reporting person

3,455,205.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

13.55 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 59318E102

1

Name of reporting person

Andrew Dakos

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,957,332.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,957,332.00

11

Aggregate amount beneficially owned by each reporting person

2,957,332.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

11.6 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock
(b)	Name of Issuer: MFS High Yield Municipal Trust
(c)	Address of Issuer's Principal Executive Offices: 111 Huntington Avenue, Boston, MASSACHUSETTS , 02199.
Item 1 Comment: This Constitutes Amendment #10 to the schedule 13D filed July 17, 2023. Except as specifically set forth herein, the schedule 13D remains unmodified.
Item 5.	Interest in Securities of the Issuer
(a)	As per the N-CSR filed on 1/23/26 there were 25,492,782 shares of common stock outstanding as of 11/30/25. The percentages set forth herein were derived using such number. Phillip Goldstein and Andrew Dakos own Bulldog Investors, LLP, a registered investment advisor. As of April 8, 2026, Bulldog Investors, LLP is deemed to be the beneficial owner of 3,072,220 shares of CMU (representing 12.05% of CMU's outstanding shares) solely by virtue of Bulldog Investors, LLP's power to direct the vote of, and dispose of, these shares. As of April 8, 2026, Mr. Goldstein is deemed to be the beneficial owner of 3,455,205 shares of CMU (representing 13.55% of CMU's outstanding shares) and Mr. Dakos is deemed to be the beneficial owner of 2,957,332 shares of CMU (representing 11.60% of CMU's outstanding shares) by virtue of their power to direct the vote of, and dispose of, these shares.
(b)	Bulldog Investors, LLP has sole power to dispose of and vote 120,488 shares. Bulldog Investors, LLP has shared power to dispose and vote 2,951,732 shares. Certain of Bulldog Investors, LLP's clients (none of whom beneficially own more than 5% of CMU's shares) share this power with Bulldog Investors. Messrs. Goldstein and Dakos are partners of Bulldog Investors, LLP.
(c)	During he last 60 days the following shares of CMU were purchased and sold. Date Shares Price 4/8/2026 (280,000) 3.6501 4/7/2026 (300,000) 3.6020 3/27/2026 10,000 3.5100 3/13/2026 (6000) 3.6426 3/11/2026 (25,900) 3.6401 3/9/2026 (14,000) 3.6400 3/6/2026 (45,000) 3.6450 3/6/2026 10,000 3.6500
(d)	Clients of Bulldog Investors, LLP and the owners of accounts reflected herein are entitled to receive any dividends or sales proceeds.
(e)	N/A
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	None
Item 7.	Material to be Filed as Exhibits.
	None

SIGNATURE

After reasonable 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.

Bulldog Investors, LLP

Signature:	/s/ Andrew Dakos
Name/Title:	Andrew Dakos, Partner
Date:	04/08/2026

Phillip Goldstein

Signature:	/s/ Phillip Goldstein
Name/Title:	Phillip Goldstein
Date:	04/08/2026

Andrew Dakos

Signature:	/s/ Andrew Dakos
Name/Title:	Andrew Dakos
Date:	04/08/2026