KAISER ALUMINUM CORP

CONSOLIDATED BALANCE SHEETS (UNAUDITED)

STATEMENTS OF CONSOLIDATED INCOME (UNAUDITED)

STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME (UNAUDITED)

STATEMENTS OF CONSOLIDATED STOCKHOLDERS’ EQUITY (UNAUDITED)

Quarter Ended March 31, 2026

At March 31, 2026,374,182 shares were available for awards under the Kaiser Aluminum Corporation 2021 Equity and Incentive Compensation Plan, as amended and restated.

Dividends declared per common share were $0.77 for the quarter ended March 31, 2026.

STATEMENTS OF CONSOLIDATED STOCKHOLDERS’ EQUITY CONTINUED (UNAUDITED)

Quarter Ended March 31, 2025

Dividends declared per common share were $0.77 for the quarter ended March 31, 2025.

STATEMENTS OF CONSOLIDATED CASH FLOWS (UNAUDITED)

See Note 11 for supplemental cash flow information.

NOTES TO INTERIM CONSOLIDATED FINANCIAL STATEMENTS - UNAUDITED

NOTES INDEX

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 ended December 31, 2025. Unless the context otherwise requires, references in these notes to interim consolidated financial statements - unaudited to “Kaiser,” “we,” “us,” “our,” “the Company” and “our Company” refer collectively to Kaiser Aluminum Corporation and its subsidiaries.

Principles of Consolidation and Basis of Presentation. The accompanying unaudited consolidated financial statements include the accounts of our wholly owned subsidiaries and are prepared in accordance with GAAP and the rules and regulations of the SEC applicable for interim periods and, therefore, do not include all information and footnotes required by GAAP for complete financial statements. In management’s opinion, all adjustments (which include normal recurring adjustments) considered necessary for a fair presentation have been included. We have reclassified certain items in prior periods to conform to current classifications. The results of operations for our interim periods are not necessarily indicative of the results of operations that may be achieved for the entire 2026 fiscal year. The financial information as of December 31, 2025 is derived from our audited consolidated financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2025.

Use of Estimates in the Preparation of Financial Statements. The preparation of financial statements in accordance with GAAP requires the use of estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities known to exist as of the date the financial statements are published and the reported amounts of revenues and expenses during the reporting period. Uncertainties with respect to such estimates and assumptions are inherent in the preparation of our consolidated financial statements; accordingly, it is possible that the actual results could differ from these estimates and assumptions, which could have a material effect on the reported amounts of our consolidated financial position and results of operations.

Adoption of New Accounting Pronouncements

Accounting for Internal-Use Software. In September 2025, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2025-06 (“ASU 2025-06”), Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software, which removes all references to software development stages so that the guidance is neutral to different software development methods. We early adopted ASU 2025-06 as of January 1, 2026 using the prospective transition approach. The adoption of ASU 2025-06 didnot have a material impact on our consolidated financial statements.

Accounting Pronouncements Issued But Not Yet Adopted

Disclosure Improvements. In October 2023, the FASB issued ASU No. 2023-06 (“ASU 2023-06”), Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. The guidance 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 becomes effective. If by June 30, 2027, the SEC does not remove the related disclosure, the pending amendment will be removed from ASC 2023-06 and it will not be effective. Adoption of ASU 2023-06 is expected to modify the disclosure and presentation requirements only and is not expected to have a material impact on our consolidated financial statements.

Disaggregation of Income Statement Expenses. In November 2024, the FASB issued ASU No. 2024-03 (“ASU 2024-03”), Disaggregation of Income Statement Expenses. The guidance requires additional, disaggregated disclosure about certain income statement expense line items. The amendments in ASU 2024-03 are effective for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027, with early adoption permitted, and is required to be applied prospectively with the option of retrospective application. We plan to adopt the provisions of ASU 2024-03 prospectively in the fourth quarter of fiscal 2027 and continue to evaluate the disclosure requirements related to the new standard.

Hedge Accounting Improvements. In November 2025, the FASB issued ASU No. 2025-09 (“ASU 2025-09”), Derivatives and Hedging (Topic 815): Hedge Accounting Improvements. The guidance introduces targeted refinements intended to improve the operability of hedge accounting and better align financial reporting with risk management activities, including greater flexibility in hedge designation and clarifications for certain instruments. ASU 2025-09 is effective for fiscal years beginning after December 15, 2026, with early adoption permitted. We are currently evaluating the impact of this pronouncement on our consolidated financial statements.

Government Grants. In December 2025, the FASB issued ASU No. 2025-10 (“ASU 2025-10”), Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities, to establish authoritative guidance on the accounting for government grants received by business entities. ASU 2025-10 is effective for fiscal years beginning after December 15, 2028, with early adoption permitted, and is required to be applied using a modified prospective, modified retrospective, or full retrospective transition method. We are currently evaluating the impact of this pronouncement on our consolidated financial statements.

Interim Reporting Narrow-Scope Improvements. In December 2025, the FASB issued ASU No. 2025-11 (“ASU 2025-11”), Interim Reporting (Topic 270): Narrow-Scope Improvements, which clarifies the scope, form and content, and required disclosures in interim financial statements prepared under GAAP. ASU 2025-11 enhances guidance for entities that issue condensed interim statements and reinstates a principles-based requirement to disclose material events since the last annual period. ASU 2025-11 is effective for interim periods in fiscal years beginning after December 15, 2027, with early adoption permitted and retrospective application optional. We are currently evaluating the impact of this standard on our consolidated financial statements.

2. Supplemental Balance Sheet Information

3. Employee Benefits

Deferred Compensation Plan

Assets of our deferred compensation plan are included in Other assets. Such assets, representing diversified investment funds in registered investment companies, are classified within Level 1 of the fair value hierarchy and are measured and recorded at fair value based on their quoted market prices. These assets are accounted for as equity investments, with changes in fair value recorded within Other expense, net (see Note 8). Offsetting liabilities relating to the deferred compensation plan are included in Other accrued liabilities and Long-term liabilities.

Short-Term Incentive Plans

As of March 31, 2026, we had a liability of$11.8 million recorded within Accrued salaries, wages and related expenses for estimated probable future payments under the 2026 short-term incentive plans.

Postretirement and Postemployment Benefit Plans

The following table presents the total expense related to all postretirement and postemployment benefit plans (in millions of dollars):

Substantially all of these charges related to employee benefits are in COGS with the remaining balance in Selling, general, administrative, research, and development (“SG&A and R&D”) in our Statements of Consolidated Income.

Deferred compensation plan expense is included within SG&A and R&D in our Statements of Consolidated Income.

The current service cost component of Net periodic postretirement and postemployment benefit cost relating to both the pension plans and the OPEB plan is included within COGS in our Statements of Consolidated Income for all periods presented. All other components are included within Other expense, net, in our Statements of Consolidated Income.

Components of Net Periodic Postretirement and Postemployment Benefit Cost. The following tables present the components of Net periodic postretirement and postemployment benefit cost relating to our defined benefit plans (in millions of dollars):

We amortize prior service cost on a straight-line basis over the average remaining years of service of the active plan participants.

4. Derivatives, Hedging Programs and Other Financial Instruments

Overview

We utilize derivative instruments to manage exposure to: (i) metal price risk related to aluminum and certain alloys used as raw material for our fabrication operations; (ii) energy price risk related to natural gas and electricity used in our production processes; and (iii) foreign currency exchange rate risk related to certain equipment and service agreements. We do not use derivative financial instruments for trading or other speculative purposes. Hedging transactions are executed centrally and are overseen by a committee (“Hedging Committee”) composed of key operations and finance personnel from the management team. Management reviews the scope of the Hedging Committee’s activities with our Board of Directors.

We are exposed to counterparty credit risk on all of our derivative instruments. Our counterparties are major investment-grade financial institutions or trading companies, and our hedging transactions are governed by negotiated International Swaps and Derivatives Association Master Agreements, which generally require collateral to be posted by our counterparties above specified credit thresholds, which may adjust up or down based on changes in counterparty credit ratings. As a result, we believe the risk of loss is remote and contained. The aggregate fair value of our derivative instruments that were in a net liability position was$1.6 million and$0.1 million at March 31, 2026 and December 31, 2025, respectively, and we hadno collateral posted as of those dates.

In addition, our firm-price customer sales commitments create incremental customer credit risk related to metal price movements. Under certain circumstances, we mitigate this risk by periodically requiring cash collateral to be posted by our customers, which we classify as deferred revenue and include as a component of Other accrued liabilities. We hadno cash collateral posted by our customers at both March 31, 2026 and December 31, 2025.

The above described derivative instruments are typically designated as cash flow hedges. Unrealized gains and losses associated with our cash flow hedges are deferred in Other comprehensive income, net of tax, and reclassified to COGS when such hedges settle or when it is probable that the original forecasted transactions will not occur by the end of the originally specified time period. See Note 7 for the total amount of gain or loss on derivative instruments designated and qualifying as cash flow hedging instruments that was reported in AOCI, as well as the related reclassifications into earnings and tax effects. Cumulative gains and losses related to cash flow hedges are reclassified out of AOCI and recorded within COGS when the associated hedged commodity purchases impact earnings.

From time to time, we enter into commodity and foreign currency forward contracts that are not designated as hedging instruments to mitigate certain short‑term impacts, as identified. The gain or loss on these commodity and foreign currency derivatives is recognized within COGS and Other expense, net, respectively. As of March 31, 2026 and December 31, 2025, we hadno outstandingnon-designated derivative hedge positions.

Notional Amount of Derivative Contracts

The following table summarizes our derivative positions at March 31, 2026:

(Gain) Loss on Derivative Contracts

The following table summarizes the amount of (gain) loss on derivative contracts recorded within our Statements of Consolidated Income in COGS (in millions of dollars):

Fair Values of Derivative Contracts

The fair values of our derivative contracts are based upon trades in liquid markets. Valuation model inputs can be verified, and valuation techniques do not involve significant judgment. The fair values of such derivatives are classified within Level 2 of the fair value hierarchy.

All of our derivative contracts with counterparties are subject to enforceable master netting arrangements. We reflect the fair value of our derivative contracts on a gross basis on our Consolidated Balance Sheets. The following table presents the fair value of our derivative financial instruments (in millions of dollars):

The following table presents the total amounts of derivative assets and liabilities on our Consolidated Balance Sheets (in millions of dollars):

Fair Values of Other Financial Instruments

All Other Financial Assets and Liabilities. We believe that the fair values of our financial assets and liabilities (accounts receivable, contract assets, current assets, accounts payable, and accrued liabilities) approximate their respective fair values due to their short maturities and nominal credit risk.

5. Debt and Credit Facility

Senior Notes

At March 31, 2026 and December 31, 2025, we had outstanding fixed-rate unsecured Senior Notes with varying maturity dates. The stated interest rates and aggregate principal amounts of such Senior Notes were, respectively: (i)4.50% and $550.0 million (“4.50% Senior Notes”) and (ii)5.875% and $500.0 million (“5.875% Senior Notes”). Our Senior Notes do not require us to make any mandatory redemptions or sinking fund payments. The following table summarizes key details of our Senior Notes:

The following table presents the fair value of our outstanding Senior Notes, which are Level 1 liabilities (in millions of dollars):

Revolving Credit Facility

In October 2019, we entered into a Revolving Credit Facility. Joining us as borrowers under the Revolving Credit Facility are four of our wholly owned domestic operating subsidiaries: (i) Kaiser Aluminum Investments Company; (ii) Kaiser Aluminum Fabricated Products, LLC; (iii) Kaiser Aluminum Washington, LLC; and (iv) Kaiser Aluminum Warrick, LLC.

As amended in October 2025, the Revolving Credit Facility is set to mature in October 2030 and contains a maximum commitment amount of $575.0 million (of which up to a maximum of $50.0 million may be utilized for letters of credit). The facility includes an accordion feature that allows for an increase in total revolving commitments of up to $200.0 million, plus an additional amount for a first-in last-out tranche, subject to lender approval and other customary conditions. The amount we can borrow under the Revolving Credit Facility is determined by the value of our eligible accounts receivable and inventory and certain other assets, which serve as collateral for the Revolving Credit Facility. Borrowings under the amended Revolving Credit Facility bear interest at a rate equal to either a base rate or the SOFR, plus, in each case, a specified variable percentage between 125 -150 basis points for SOFR loans (or 25 -50 basis points for base rate loans) determined by reference to the then-remaining borrowing availability under the Revolving Credit Facility and, in certain instances, a fixed margin. Outstanding borrowings under the Revolving Credit Facility are reported within Long-term debt, net, on our Consolidated Balance Sheets. We hadno outstanding borrowings under the Revolving Credit Facility as of March 31, 2026 and $22.3 million of outstanding borrowings under the Revolving Credit Facility as of December 31, 2025.

The following table summarizes availability and usage of our Revolving Credit Facility as determined by a borrowing base calculated as of March 31, 2026 (in millions of dollars):

Interest Expense

The following table presents interest expense relating to our Senior Notes and Revolving Credit Facility (in millions of dollars):

6. Commitments and Contingencies

Commitments. We have a variety of financial commitments, including purchase agreements, forward foreign exchange and forward sales contracts, indebtedness and letters of credit (see Note 4 and Note 5).

Environmental Contingencies. We are subject to several environmental laws and regulations, potential fines or penalties assessed for alleged breaches of such laws and regulations, and potential claims based upon such laws and regulations. We are also subject to legacy environmental contingencies related to activities that occurred at our operating facilities prior to July 6, 2006, which represent the majority of our environmental accruals of$17.7 million as of March 31, 2026. This accrual represents our undiscounted estimate of costs reasonably expected to be incurred based on current laws and regulations, available facts, existing technologies, and our assessment of the likely remediation actions to be taken.

Based on approved and proposed remediation action plans for the various facilities, we expect that the implementation and ongoing monitoring could occur over a period of 30 or more years. As additional facts are developed, feasibility studies are completed, remediation plans are modified, necessary regulatory approvals for the implementation of remediation are obtained, alternative technologies are developed and/or other factors change, there may be revisions to management’s estimates, and actual costs may exceed the current environmental accruals by up to$14.2 million. Changes to our estimates may occur within the next 12 months as new information becomes available.

Other Contingencies. We are party to various lawsuits, claims, investigations and administrative proceedings that arise in connection with past and current operations. We evaluate such matters on a case-by-case basis and our policy is to vigorously contest any such claims we believe are without merit. We accrue for a legal liability when it is both probable that a liability has been incurred and the amount of the loss is reasonably estimable. Quarterly, in addition to when changes in facts and circumstances require it, we review and adjust these accruals to reflect the impacts of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. While uncertainties are inherent in the final outcome of such matters and it is presently impossible to determine the actual cost that may ultimately be incurred, we believe that we have sufficiently accrued for such matters and that the ultimate resolution of pending matters will not have a material impact on our consolidated financial position, operating results or liquidity.

7. Accumulated Other Comprehensive Income

The following table presents the changes in the accumulated balances for each component of AOCI (in millions of dollars):

Amounts amortized out of AOCI related to pension and other postretirement and postemployment benefits were included within Net periodic postretirement and postemployment benefit cost (see Note 3).

Income tax amounts reclassified out of AOCI were included as a component of Income tax provision.

As of March 31, 2026, we estimate a net mark-to-market gain before tax of$13.0 million in AOCI will be reclassified into Net income upon settlement within the next 12 months.

8. Other Expense, Net

The following table presents the components of Other expense, net (in millions of dollars):

Supply Chain Financing. We are party to several supply chain financing arrangements, in which we may sell certain of our customers’ trade accounts receivable to such customers’ financial institutions without recourse. During the quarter March 31, 2026 and March 31, 2025, we sold trade accounts receivable totaling$295.2 million and$270.0 million, respectively, related to these supply chain financing arrangements, of which our customers’ financial institutions applied discount fees totaling$6.5 million and$5.6 million, respectively. To the extent discount fees related to the sale of trade accounts receivable under supply chain financing arrangements are not reimbursed by our customers, they are included in Other expense, net. As of March 31, 2026, we had been and/or expected to be substantially reimbursed by our customers for these discount fees, in accordance with the underlying sales agreements.

9. Income Tax Matters

The following table presents the income tax provision by region (in millions of dollars):

The income tax provision for the quarters ended March 31, 2026 and March 31, 2025 was$19.9 million and$7.2 million, respectively, reflecting an effective tax rate of 24% and 25%, respectively. There was no material difference between the effective tax rate and the blended statutory tax rate for the quarters ended March 31, 2026 and 2025.

Our gross unrecognized benefits relating to uncertain tax positions were$7.7 millionand $7.4 million at March 31, 2026 and December 31, 2025, respectively. If recognized, these amounts would be reflected in our income tax provision and affect our effective tax rate.

10. Earnings Per Share

Basic net income per share is computed by dividing distributed and undistributed net income allocable to common shares by the weighted-average number of common shares outstanding during the applicable period. The basic weighted-average number of common shares outstanding during the period excludes non-vested share-based payment awards. Basic and diluted net income per share was calculated under the two-class method for the quarters ended March 31, 2026 and 2025.

The following table sets forth the computation of basic and diluted net income per share (in millions of dollars, except share and per share amounts):

Represents Net income less distributed and undistributed earnings allocated to non-vested restricted stock awards that contain non-forfeitable rights to dividends.

Quantities in the following discussion are denoted in whole shares. During thequarters ended March 31, 2026 and 2025, approximately 500 and 4,000 shares, respectively, were excluded from the weighted-average diluted shares computation as their inclusion would have been anti‑dilutive.

11. Supplemental Cash Flow Information

We are required to keep on deposit certain amounts that are pledged or held as collateral relating to workers’ compensation and other agreements. We account for such deposits as restricted cash. From time to time, such restricted funds could be returned to us or we could be required to pledge additional cash.

12. Business, Product, and Geographical Area Information

Ourprimary line of business is the production of semi-fabricated specialty aluminum mill products, such as plate and sheet, bare and coated coils, and extruded and drawn products, primarily used in our Aero/HS Products, Packaging, GE Products, and Automotive

Extrusionsend markets. We operate production facilities in the United States and Canada. We haveone operating and reportable segment. Our determination that we operate as a single segment is consistent with the financial information regularly viewed by the chief operating decision maker (“CODM”) to evaluate performance and make decisions regarding resource allocation. The CODM uses Net income to measure segment profitability in deciding whether to reinvest profits into the segment or into other parts of the entity, such as for acquisitions or to pay dividends.

The following table presents the significant segment expenses that are provided to the CODM (in millions of dollars):

Hedged cost of alloyed metal includes cost of aluminum at the MWTP and the cost of alloying elements used in the production process. This metric also includes metal price exposure on shipments that we hedged with realized gains upon settlement of $7.5 million and $4.6 million in the quarters ended March 31, 2026 and March 31, 2025, respectively.

Manufacturing costs primarily includes labor, utilities, supplies, metal valuation impacts, metal profits, and other materials, excluding alloys, incurred at our various production facilities.

Plant overhead includes salaried employee costs, property taxes, and insurance associated with our various production facilities.

Other cost of products sold primarily includes accretion expense related to conditional asset retirement obligations, gains and losses on operating asset disposals, and major maintenance costs.

Employee costs include indirect labor salaries, benefits, and incentive compensation.

Other selling, general and administrative costs primarily includes professional services, computer hardware and software costs, office rent, and utilities.

The CODM does not review asset and capital expenditure information by reportable operating segment as such information is presented to the CODM on a consolidated basis.

The following table presents Net sales by end market applications and by timing of control transfer (in millions of dollars):

The following table presents geographic information for income taxes paid (in millions of dollars):

13. Subsequent Events

Dividend Declaration. On April 13, 2026, we announced that our Board of Directors declared a quarterly cash dividend of$0.77 per common share. As such, we expect to pay approximately$12.8 million (including dividend equivalents) on or about May 15, 2026 to stockholders of record and the holders of certain restricted stock units at the close of business on April 24, 2026.