Momentus Inc.

Item 4.01 Changes in Registrant’s Certifying Accountant. (a) Dismissal of Independent Registered Public Accounting Firm On August 10 2026, the Audit Committee of the Board of Directors (the “Audit Committee”) of Momentus Inc. (the “Company”) approved the dismissal of Frank, Rimerman + Co. LLP (“Frank, Rimerman”) as the Company’s independent registered public accounting firm, effective August 11, 2026. Frank, Rimerman's report on the Company's consolidated financial statements as of and for the year ended December 31, 2025 did not contain an adverse opinion or disclaimer of opinion and was not qualified or modified as to uncertainty, audit scope or accounting principles. Frank, Rimerman's report on the Company's consolidated financial statements as of and for the year ended December 31, 2024 did not contain an adverse opinion or disclaimer of opinion and was not qualified or modified as to audit scope or accounting principles, but included an explanatory paragraph regarding substantial doubt about the Company's ability to continue as a going concern. During the Company’s fiscal years ended December 31, 2025 and 2024 and the subsequent interim period through August 11, 2026, there were no disagreements with Frank, Rimerman on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreement(s), if not resolved to the satisfaction of Frank, Rimerman, would have caused it to make reference to the subject matter of the disagreement(s) in connection with its report. During the Company’s fiscal years ended December 31, 2025 and 2024 and the subsequent interim period through August 11, 2026, there were no reportable events of the type described in Item 304(a)(1)(v) of Regulation S-K, except that, as reported in Part II, Item 9A, Controls and Procedures, in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2024, the Company identified a material weakness in its internal control over financial reporting related to misclassification errors in its accounting for certain matters. As subsequently disclosed in Item 9A, Controls and Procedures, of the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (the “2025 Form 10-K”), the Company remediated this material weakness as of December 31, 2025, through the implementation of internal control enhancements and ongoing monitoring and testing. Please refer to the disclosure contained in Item 9A, Controls and Procedures, of the 2025 Form 10-K for additional information regarding such remediation. The Audit Committee discussed the reportable event described above with Frank, Rimerman, and the Company has authorized Frank, Rimerman to respond fully to the inquiries of Baker Tilly concerning this reportable event. The Company provided Frank, Rimerman with a copy of the foregoing disclosure and requested Frank, Rimerman to furnish the Company with a letter addressed to the U.S. Securities and Exchange Commission (the “SEC”) stating whether it agrees with the statements made therein. A copy of such letter furnished by Frank, Rimerman is filed as Exhibit 16.1 to this Form 8-K. (b) Engagement of New Independent Registered Public Accounting Firm On August 10, 2026, the Company’s Audit Committee appointed Baker Tilly US, LLP (“Baker Tilly”) as the Company’s new independent registered public accounting firm, effective upon execution of the engagement agreement with Baker Tilly. On August 12, 2026, the engagement agreement was executed by the Company and Baker Tilly, and Baker Tilly was engaged as the independent registered public accounting firm. During the Company’s two most recent fiscal years and the subsequent interim period through August 11, 2026, neither the Company nor anyone on its behalf consulted with Baker Tilly regarding (i) the application of accounting principles to a specified transaction, either completed or proposed; the type of audit opinion that might be rendered on the Company’s financial statements, and neither a written report nor oral advice was provided that Baker Tilly concluded was an important factor considered by the Company in reaching a decision as to the accounting, auditing or financial reporting issue; or (ii) any matter that was either the subject of a disagreement (as defined in Item 304(a)(1)(iv) of Regulation S-K and its related instructions) or a reportable event (as described in Item 304(a)(1)(v) of Regulation S‑K).