FORM10-Q ☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934For the transition period from __________ to __________ KAISER ALUMINUM CORPORATION 94-3030279(I.R.S. Employer Identification No.) 37067(Zip Code) Title of each classCommon stock, par value $0.01 per share Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities ExchangeAct of 1934 during the preceding 12 months, and (2) has been subject to such filing requirements for the past 90 days.Yes☒No☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant toRule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reportingcompany, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and Large accelerated filerNon-accelerated filer If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complyingwith any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes☐No☒ As of April 21, 2025, there were16,154,376shares of common stock of the registrant outstanding. TABLE OF CONTENTS PART IIItem 1. Legal Proceedings38Item 1A. Risk Factors38Item 2. Unregistered Sales of Equity Securities and Use of Proceeds38Item 3. Defaults Upon Senior Securities38Item 4. Mine Safety Disclosures38Item 5. Other Information38Item 6. Exhibits40SIGNATURES41 The accompanying notes to interim consolidated financial statements are an integral part of these statements. 1. Basis of Presentation and Recent Accounting Pronouncements This Form 10-Q should be read in conjunction with the Company’s Annual Report on Form 10-K for the year endedDecember 31, 2024. Unless the context otherwise requires, references in these notes to interim consolidated financial statements - Principles of Consolidation and Basis of Presentation.The accompanying unaudited consolidated financial statementsinclude the accounts of our wholly owned subsidiaries and are prepared in accordance with GAAP and the rules and regulations ofthe SEC applicable for interim periods and, therefore, do not include all information and footnotes required by GAAP for completefinancial statements. In management’s opinion, all adjustments (which include normal recurring adjustments) considered necessaryfor a fair presentation have been included. We have reclassified certain items in prior periods to conform to current classifications. Use of Estimates in the Preparation of Financial Statements.The preparation of financial statements in accordance withGAAP requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure ofcontingent assets and liabilities known to exist as of the date the financial statements are published and the reported amounts of Change in Accounting Principle.Effective January 1, 2025, the Company changed its inventory valuation methodology fromLIFO to WAC for its finished products, work-in-process, and raw material inventories. This change is preferable because theCompany believes that it improves the comparability of the Company's operational results between periods by removing LIFOincome or charge in a period resulting from LIFO valuation and changes to historical LIFO layers. Additionally, the Companybelieves that the new valuation methodology better reflects the physical flow of goods and simplifies the financial close process by Accounting Pronouncements Issued But Not Yet Adopted Disclosure Improvements.In October 2023, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2023-06(“ASU 2023-06”), Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. Theguidance amends GAAP to reflect updates and simplifications to certain disclosure requirements referred to the FASB by the SEC.The amendments in ASU 2023-06 will become effective on the date which the SEC’s removal of the related disclosure becomeseffective. If by June 30, 2027, the SEC does not remove the related disclosure, the pending amendment will be removed from ASC Income Taxes.In December 2023, the FASB issued ASU No. 2023-09 (“ASU 2023-09”), Improvements to Income TaxDisclosures. The guidance is intended to improve income tax disclosure requirements by requiring: (i) consistent categories andgreater disaggregation of informa