Mayville Engineering Company, Inc.

Evaluation of Disclosure Controls and Procedures

We maintain disclosure controls and procedures that are designed to provide reasonable assurance that information required to be disclosed in the reports we file or submit under the Securities Exchange Act of 1934, as amended (the Exchange Act), is recorded, processed, summarized and reported within the time periods specified in the rules and forms of the SEC, and that such information is accumulated and communicated to our management, including our Chief Executive Officer and Chief Financial Officer, to allow for timely decisions regarding required disclosure. In designing disclosure controls and procedures, our management necessarily was required to apply its judgment in evaluating the cost-benefit relationship of possible disclosure controls and procedures. The design of any disclosure controls and procedures also is based in part upon certain assumptions about the likelihood of future events, and there can be no assurance that any design will succeed in achieving its stated goals under all potential future conditions. Any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving the desired objectives.

As of September 30, 2025, we carried out an evaluation, under the supervision and with the participation of our Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act). Based on this evaluation, our Chief Executive Officer and Chief Financial Officer concluded that, due to the identification of the material weakness in our internal control over financial reporting as described below, our disclosure controls and procedures were not effective as of September 30, 2025. Notwithstanding the material weakness in our internal control over financial reporting, management believes the condensed consolidated financial statements included in this Quarterly Report on Form 10-Q fairly present, in all material respects, our financial position, results of operations and cash flows as of the dates presented, and for the periods ended on such dates, in conformity with accounting principles generally accepted in the United States of America (GAAP).

Remediation of Previously Identified Material Weakness

A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of our annual or interim condensed consolidated financial statements will not be prevented or detected on a timely basis.

As previously described in Part II, Item 9A of our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, Management identified deficiencies in the design and operating effectiveness of internal control over financial reporting related to the review and approval of journal entries that constitutes a material weakness.

Subsequent to the identification of the material weakness, management under the oversight of the Audit Committee has been implementing measures and taking steps to address the underlying causes of the material weakness. Specifically, the following remediation efforts are planned or ongoing to ensure adequate review and approval of journal entries, including:

While we believe these efforts have improved our internal controls and address the underlying cause of the material weakness, the material weakness will not be remediated until our remediation plan has been fully implemented and tested and we have concluded that following the improvements to our internal controls, our control environment is operating effectively for a sufficient period of time. In particular, the enhanced compensating controls and training will require time to test and assess. We cannot be certain that the steps we are taking will be sufficient to remediate the control deficiencies that led to the material weakness in our internal control over financial reporting or prevent future material weaknesses or control deficiencies from occurring. In addition, we cannot be certain that we have identified all material weaknesses in our internal control over financial reporting, or that in the future we will not have additional material weaknesses in our internal control over financial reporting.

Changes in Internal Control Over Financial Reporting

In connection with the acquisition of Accu-Fab in July 2025, we are in the process of reviewing the internal control structure of Accu-Fab and, if necessary, will make appropriate changes as we continue to integrate Accu-Fab into our overall internal control over financial reporting process.

Except for the acquisition of Accu-Fab and the remediation efforts related to the previously identified material weakness, there were no changes in our internal control over financial reporting that occurred during the quarter ended September 30, 2025, that materially affected, or were reasonably likely to materially affect, our internal control over financial reporting.