RiverNorth reports 11.60% stake in MFS High Yield Trust

RiverNorth Capital Management filed an amendment to a Schedule 13G reporting beneficial ownership of 2,955,950 shares of MFS High Yield Municipal Trust (CUSIP 59318E102), representing 11.60% of the class as of 03/31/2026.

Rhea-AI Filing Summary

RiverNorth Capital Management filed an amendment to a Schedule 13G reporting beneficial ownership of 2,955,950 shares of MFS High Yield Municipal Trust (CUSIP 59318E102), representing 11.60% of the class as of 03/31/2026. The filing lists sole voting and dispositive power over all reported shares. The amendment is signed by Marcus Collins, General Counsel and Chief Compliance Officer, dated 05/15/2026.

Insights

Institutional Ownership Analyst

Large passive holding disclosed: RiverNorth reports 11.60% ownership.

RiverNorth Capital Management reports beneficial ownership of 2,955,950 shares of MFS High Yield Municipal Trust as of 03/31/2026. The filing shows sole voting and dispositive power for the full position, indicating direct control over voting and disposition decisions on these shares.

Timing and trading intent are not provided in the excerpt; subsequent transaction activity would appear in later schedules if any sales or acquisitions occur.

Compliance Counsel

Amendment formalizes ownership disclosure and authority.

The Schedule 13G/A amendment updates Items including name, address, citizenship, and the ownership table showing 11.60% of the class. It records sole voting and dispositive powers of 2,955,950 shares, satisfying Schedule 13G reporting structure for large passive or qualifying holders.

The signature by the General Counsel on 05/15/2026 provides the required attestation to the amended filing.

Key Figures

Shares beneficially owned: 2,955,950 shares Percent of class: 11.60% CUSIP: 59318E102 +2 more

5 metrics

Shares beneficially owned 2,955,950 shares Amount reported in Item 4(a)

Percent of class 11.60% Percent of class reported as of 03/31/2026

CUSIP 59318E102 Security identifier for Shares of Beneficial Interest

Ownership date 03/31/2026 Date tied to the ownership amount

Filing signature date 05/15/2026 Date the amendment was signed by Marcus Collins

Key Terms

Schedule 13G/A, Beneficial ownership, Sole dispositive power

3 terms

Schedule 13G/A regulatory

"Amendment to Schedule 13G reporting beneficial ownership"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficial ownership financial

"Amount beneficially owned: 2,955,950 (b) Percent of class: 11.60%"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

Sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 2,955,950"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does RiverNorth (CMU) report in MFS High Yield Municipal Trust?

RiverNorth reports beneficial ownership of 2,955,950 shares, equal to 11.60% of the class as of 03/31/2026. The filing states RiverNorth has sole voting and dispositive power over these shares.

When was the Schedule 13G/A amendment for CMU filed and signed?

The amendment is signed by Marcus Collins, General Counsel, and dated 05/15/2026. The reported ownership amount is stated with an ownership date of 03/31/2026 in the filing.

Does the filing indicate RiverNorth manages these shares for others?

The filing notes that other persons have the right to receive proceeds from sales, indicating shares may be held on behalf of clients or funds. No specific third-party beneficiaries are identified in the excerpt.

What voting and disposition powers does RiverNorth claim in the filing?

The Schedule 13G/A reports RiverNorth has sole power to vote and sole power to dispose of all 2,955,950 shares noted. Shared voting and dispositive powers are reported as 0.

What is the CUSIP and class of the securities reported in this filing?

The securities are Shares of Beneficial Interest of MFS High Yield Municipal Trust with CUSIP 59318E102, as stated in Item 1 and Item 2 of the Schedule 13G/A amendment.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/15/2026 - 12:54 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

MFS HIGH YIELD MUNICIPAL TRUST

(Name of Issuer)

Shares of Beneficial Interest

(Title of Class of Securities)

59318E102

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 59318E102

1

Names of Reporting Persons

RIVERNORTH CAPITAL MANAGEMENT, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 2,955,950.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,955,950.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,955,950.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

11.6 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MFS HIGH YIELD MUNICIPAL TRUST
(b)	Address of issuer's principal executive offices: 111 HUNTINGTON AVENUE, 24TH FLOOR, BOSTON, MA, 02199
Item 2.
(a)	Name of person filing: RiverNorth Capital Management, LLC
(b)	Address or principal business office or, if none, residence: 360 S. Rosemary Avenue, Ste. 1420 West Palm Beach, Florida 33401
(c)	Citizenship: Delaware
(d)	Title of class of securities: Shares of Beneficial Interest
(e)	CUSIP No.: 59318E102
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2,955,950
(b)	Percent of class: 11.60%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 2,955,950
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2,955,950
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Other persons have the right to receive the proceeds from the sale of the securities reported herein.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. Not applicable.
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. Not applicable.
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. Not applicable.

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

RIVERNORTH CAPITAL MANAGEMENT, LLC

Signature:	/s/ Marcus Collins
Name/Title:	Marcus Collins, General Counsel and Chief Compliance Officer
Date:	05/15/2026