8-K

UNITED

STATES

SECURITIES

AND EXCHANGE COMMISSION

Washington,

D.C. 20549

FORM

8-K

CURRENT

REPORT

Pursuant

to Section 13 or 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March29, 2026

SOLUNA

HOLDINGS, INC.

(Exactname of registrant as specified in its charter)

Registrant’sTelephone Number, Including Area Code: (516) 216-9257

N/A

(FormerName or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions(see General Instruction A.2. below):

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.

Item4.01. Changes in Registrant’s Certifying Accountant.

(a)Dismissal of Independent Registered Public Accounting Firm.

On March 29, 2026, Soluna Holdings, Inc. (the “Company”) notified UHY LLP (“UHY”) that UHY would be dismissed as the Company’s independent registered public accounting firm. The Audit Committee of the Board of Directors of the Company (the “Audit Committee”) approved the decision to dismiss UHY, which will become effective on March 29, 2026.

The audit reports of UHY on the Company’s financial statements as of and for the fiscal years ended December 31, 2025 and 2024 did not contain an adverse opinion or a disclaimer of opinion, and were not qualified or modified as to uncertainty, audit scope, or accounting principles.

During the Company’s two most recent fiscal years ended December 31, 2025 and 2024, and through March 29, 2026, the Company has not had any disagreement with UHY on any matter of accounting principles or practices, financial statement disclosure or auditing scope or procedures, which disagreement, if not resolved to UHY’s satisfaction, would have caused UHY to make reference to the subject matter of the disagreement in its reports on the Company’s financial statements. In addition, during the Company’s two most recent fiscal years ended December 31, 2025 and 2024, and through March 29, 2026, there were no “reportable events” as that term is defined in Item 304(a)(1)(v) of Regulation S-K.

The Company provided UHY with a copy of this Current Report on Form 8-K prior to its filing with the Securities and Exchange Commission (“SEC”) and requested that UHY furnish it with a letter addressed to the SEC stating whether or not it agrees with the above statements in this Item 4.01(a). A copy of UHY’s letter, dated March 30, 2026, is filed as Exhibit 16.1 to this Current Report on Form 8-K.

(b)Appointment of New Independent Registered Public Accounting Firm.

On March 29, 2026, the Audit Committee approved the appointment of KPMG LLP (“KPMG”) as the Company’s new independent registered public accounting firm for the fiscal year ended December 31, 2026.

During the fiscal years ended December 31, 2025 and 2024 and the subsequent interim period through March 29, 2026, neither the Company nor anyone acting on its behalf consulted KPMG on any matter relating to either (i) the application of accounting principles to a specific transaction, either completed or contemplated, or the type of audit opinion that might be rendered on the Company’s financial statements or (ii) any matter that was the subject of a disagreement (as that term is defined in Item 304(a)(1)(iv) of Regulation S-K and the related instructions) or a “reportable event” (as that term is defined in Item 304(a)(1)(v) of Regulation S-K).

Item9.01. Financial Statements and Exhibits.

(d) Exhibits

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Exhibit16.1

March 30, 2026

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Commissioners:

We have read Item 4.01 of Form 8-K filed with the U.S. Securities and Exchange Commission on March 30, 2026 of Soluna Holdings, Inc. (the “Company”) and are in agreement with the statements contained in (a) (Dismissal of Independent Registered Public Accounting Firm). We have no basis to agree or disagree with other statements of the Company contained therein.

/s/ UHY LLP

Albany, New York

March 30, 2026