Goldstein and Dakos adjust MFS High Yield Municipal (CMU) holdings

Rhea-AI Filing Summary

MFS High Yield Municipal Trust received an updated Schedule 13D/A (Amendment No. 12) from Bulldog Investors, LLP and its principals Phillip Goldstein and Andrew Dakos. Based on 25,492,782 shares outstanding as of 11/30/25, Bulldog Investors is deemed the beneficial owner of 2,459,393 shares, or 9.65% of the common stock. Goldstein is deemed to beneficially own 2,842,378 shares, or 11.15% of the company, while Dakos is deemed to beneficially own 2,344,505 shares, or 9.20%. The filing notes recent CMU share sales between 4/24/26 and 4/29/26 at prices around $3.65 per share, executed through Bulldog-managed accounts. Clients of Bulldog Investors and the account owners are entitled to any dividends or sales proceeds.

Insights

Closed-end fund governance analyst

Bulldog and principals report sizeable, slightly reduced CMU stakes with routine trading activity.

The amendment shows Bulldog Investors, LLP and partners Phillip Goldstein and Andrew Dakos maintaining large positions in MFS High Yield Municipal Trust. Goldstein’s reported beneficial stake is 2,842,378 shares, or 11.15%, while Bulldog holds 2,459,393 shares, or 9.65%.

Item 5 details several CMU share sales from April 24–29, 2026 at prices near $3.65 per share. These transactions modestly reduce their holdings but leave them well above typical disclosure thresholds, indicating continued significant ownership and influence potential.

The filing characterizes Bulldog as having both sole and shared voting and dispositive power over portions of the position, with certain clients sharing this power. Subsequent filings may clarify whether trading patterns or ownership percentages change meaningfully over time.

Key Figures

Shares outstanding: 25,492,782 shares Bulldog Investors beneficial ownership: 2,459,393 shares (9.65%) Phillip Goldstein beneficial ownership: 2,842,378 shares (11.15%) +3 more

6 metrics

Shares outstanding 25,492,782 shares Common stock outstanding as of 11/30/25 per N-CSR

Bulldog Investors beneficial ownership 2,459,393 shares (9.65%) Beneficial ownership of CMU as of 04/29/26

Phillip Goldstein beneficial ownership 2,842,378 shares (11.15%) Beneficial ownership of CMU as of 04/29/26

Andrew Dakos beneficial ownership 2,344,505 shares (9.20%) Beneficial ownership of CMU as of 04/29/26

Largest single disclosed sale 125,302 shares at $3.6516 CMU sale on 04/28/2026

Sample sale price $3.6500 per share CMU sale price on 04/24/2026

Key Terms

Schedule 13D/A, beneficial owner, voting power, dispositive power, +1 more

5 terms

Schedule 13D/A regulatory

"This Constitutes Amendment #12 to the filed July 17, 2023."

A Schedule 13D/A is an amended disclosure filed with regulators by an investor who already reported owning more than 5% of a company’s shares and needs to update their original filing. Think of it as a public status update that tells markets whether the investor’s ownership, plans, or source of funds have changed; such updates matter because they can signal a push for control, major strategic moves, or increased pressure on management, which can affect stock prices.

beneficial owner financial

"Bulldog Investors, LLP is deemed to be the beneficial owner of 2,459,393 shares"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

voting power financial

"Bulldog Investors, LLP has sole power to dispose of and vote 120,488 shares."

Voting power is the ability shareholders have to influence a company's major decisions—like electing the board, approving mergers, or changing corporate rules—based on the voting rights attached to the shares they hold. For investors it matters because greater voting power is like holding more keys to a building: it gives you a stronger say over management choices and the company’s strategy, which can affect future value and risk.

dispositive power financial

"Bulldog Investors, LLP has shared power to dispose and vote 2,338,905 shares."

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

registered investment advisor financial

"Phillip Goldstein and Andrew Dakos own Bulldog Investors, LLP, a registered investment advisor."

A registered investment advisor is a professional or firm that provides financial advice and manages investments for clients, operating under regulations that require them to act in their clients' best interests. This designation helps investors identify trustworthy advisors who are legally committed to providing transparent and fair guidance, much like a licensed doctor is bound to prioritize patient well-being.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 12)

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)

04/29/2026

(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 2,338,905.00
9	Sole Dispositive Power 120,488.00
10	Shared Dispositive Power 2,338,905.00

11

Aggregate amount beneficially owned by each reporting person

2,459,393.00

12

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

13

Percent of class represented by amount in Row (11)

9.65 %

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 2,721,890.00
9	Sole Dispositive Power 120,488.00
10	Shared Dispositive Power 2,721,890.00

11

Aggregate amount beneficially owned by each reporting person

2,842,378.00

12

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

13

Percent of class represented by amount in Row (11)

11.15 %

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 2,344,505.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,344,505.00

11

Aggregate amount beneficially owned by each reporting person

2,344,505.00

12

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

13

Percent of class represented by amount in Row (11)

9.2 %

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 #12 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 29, 2026, Bulldog Investors, LLP is deemed to be the beneficial owner of 2,459,393 shares of CMU (representing 9.65% 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 29, 2026, Mr. Goldstein is deemed to be the beneficial owner of 2,842,378 shares of CMU (representing 11.15% of CMU's outstanding shares) and Mr. Dakos is deemed to be the beneficial owner of 2,344,505 Shares of CMU (representing 9.20% 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 2,338,905 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)	Since the last filing on 4/27/26 the following shares of CMU were sold. Date Shares Price 4/24/2026 (18,468) 3.6500 4/27/2026 (27,600) 3.6530 4/27/2026 (75,000) 3.6600 4/28/2026 (125,302) 3.6516 4/29/2026 (75,000) 3.6484 4/29/2026 (31,916) 3.6568"
(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:	04/30/2026

Phillip Goldstein

Signature:	/s/ Phillip Goldstein
Name/Title:	Phillip Goldstein
Date:	04/30/2026

Andrew Dakos

Signature:	/s/ Andrew Dakos
Name/Title:	Andrew Dakos
Date:	04/30/2026

FAQ

What ownership stake in CMU does Bulldog Investors report in this Schedule 13D/A?

Bulldog Investors, LLP reports beneficial ownership of 2,459,393 CMU shares, representing 9.65% of the common stock. This percentage is calculated using 25,492,782 shares outstanding as of November 30, 2025, as disclosed in the issuer’s N-CSR filing.

How many CMU shares is Phillip Goldstein deemed to beneficially own?

Phillip Goldstein is deemed to beneficially own 2,842,378 CMU shares, or 11.15% of the outstanding common stock. This reflects both his direct holdings and his indirect power to direct the vote and disposition of shares through Bulldog Investors and related accounts.

What is Andrew Dakos’s reported beneficial ownership in CMU?

Andrew Dakos is deemed to beneficially own 2,344,505 CMU shares, representing 9.20% of the outstanding common stock. He shares voting and dispositive power over these shares, primarily through his role as a partner of Bulldog Investors, LLP as described in the filing.

What recent CMU share sales are disclosed in this amendment?

The filing lists several CMU sales between April 24 and April 29, 2026, including 125,302 shares at $3.6516 on April 28, 2026. Other sales occurred at prices around $3.65 per share, reflecting routine trading in accounts managed by Bulldog Investors.

How many CMU shares are outstanding for calculating these ownership percentages?

Ownership percentages use 25,492,782 CMU shares outstanding as of November 30, 2025. This share count comes from the issuer’s N-CSR filed on January 23, 2026, and serves as the denominator for all percentage-of-class calculations in the amendment.

Who is entitled to dividends and sale proceeds from the CMU shares managed by Bulldog Investors?

According to the filing, clients of Bulldog Investors, LLP and the owners of the accounts are entitled to receive any dividends or sales proceeds. Bulldog and its partners primarily exercise voting and dispositive power over the shares on behalf of these clients.