KAISER ALUMINUM CORP New Standards Disclosure

Adoption of New Accounting Pronouncements

Income Taxes. In December 2023, the FASB issued ASU No. 2023-09 (“ASU 2023-09”), Improvements to Income Tax Disclosures. The guidance is primarily intended to improve income tax disclosure requirements by requiring (i) consistent categories and greater disaggregation of information in the rate reconciliation and (ii) the disaggregation of income taxes paid by jurisdiction. The guidance makes several other changes to the income tax disclosure requirements. The amendments in ASU 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and is required to be applied prospectively with the option of retrospective application. We adopted ASU 2023-09 effective December 31, 2025 using a retrospective approach. See Note 14 for the required disclosures related to our adoption of ASU 2023-09. This standard update did not affect our operating results.

Credit Losses for Accounts Receivable and Contract Assets. In July 2025, the FASB issued ASU No. 2025-05 (“ASU 2025-05”), Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets, which provides entities with a practical expedient to simplify the estimation of expected credit losses by assuming that the current conditions as of the balance sheet date will not change for the remaining life of the asset. We adopted ASU 2025-05 effective December 31, 2025 using a prospective approach. The adoption of this ASU did not have a material impact on our consolidated financial statements.