Mayville Engineering Company, Inc. New Standards Disclosure

Recently adopted accounting pronouncements

In December 2023, the FASB issued Accounting Standards Update (ASU) 2023-09, Improvements to Income Tax Disclosures, amending ASC 740, Income Taxes. The amendment is intended to enhance the transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The amendments require that on an annual basis, entities disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, the amendments require that entities disclose additional information about income taxes paid as well as additional disclosures of pretax income and income tax expense and remove the requirement to disclose certain items that are no longer considered cost beneficial or relevant. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company adopted this standard in the fourth quarter of 2025 and the amendments have been applied on a retrospective basis. Adoption of ASU 2023-09 did not have a material impact on the Company’s consolidated financial statements.

Recently issued accounting standards not yet adopted

In November 2024, the FASB issued ASU 2024-03, Expense Disaggregation Disclosures, amending ASC 220, Income Statement – Reporting Comprehensive Income. The amendment requires an entity to provide a disclosure within the financial statement footnotes showing the disaggregation of certain expenses included in relevant expense captions on the consolidated income statement, with a qualitative description of the amounts that are not separately disaggregated quantitatively. The guidance also requires disclosure of the total amount of selling expenses and, in annual reporting periods, an entity’s definition of selling expenses. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026 and for interim periods beginning after December 15, 2027. The guidance is applied on a prospective basis, with a retrospective option and allows for early adoption. The Company is evaluating the potential impact of this guidance on the consolidated financial statements.

In September 2025, the FASB issued ASU 2025-06, Intangibles – Goodwill and Other-Internal-Use Software, amending ASC 350. The amendment removes all references to prescriptive and sequential software development stages. In addition, the amendment also requires consideration whether there is significant uncertainty associated with the development activities of the software during evaluation of probable-to-complete recognition threshold. ASU 2025-06 is effective for interim and annual periods beginning after December 15, 2027. Entities may adopt the guidance using either a prospective approach (including a modified transition approach) or retrospective approach. Early adoption is permitted. The Company has early adopted ASU 2025-06 on a prospective basis, as of January 1, 2026. The adoption of the ASU is not expected to have a material impact on the Company’s consolidated financial statements.

In December 2025, the FASB issued ASU 2025-11, Interim Reporting - Narrow-Scope Improvements, amending ASC 270. The ASU clarifies interim disclosure requirements and the applicability of ASC 270. The objective of the amendments is to provide further clarity about the current interim disclosure requirements. The ASU is effective for interim reporting periods within annual reporting

periods beginning after December 15, 2027. Adoption of this ASU can be applied either a prospective or a retrospective approach. Early adoption is permitted. The Company is evaluating the potential impact of this guidance on the consolidated financial statements.

In December 2025, the FASB issued ASU 2025-12, Codification Improvements. The ASU addresses thirty-three items, representing the changes to the Codification that (1) clarify, (2) correct errors, or (3) make minor improvements. Generally, the amendments in this Update are not intended to result in significant changes for most entities. The ASU is effective for interim reporting periods within annual reporting periods beginning after December 15, 2026. Early adoption is permitted. The Company is evaluating the potential impact of this guidance on the consolidated financial statements.