KAISER ALUMINUM CORP

To the shareholders and the Board of Directors of Kaiser Aluminum Corporation

Opinions on the Financial Statements and Internal Control over Financial Reporting

We have audited the accompanying consolidated balance sheets of Kaiser Aluminum Corporation and subsidiaries (the "Company") as of December 31, 2024 and 2023, the related consolidated statements of income (loss), comprehensive income (loss), stockholders' equity, and cash flows, for each of the three years in the period ended December 31, 2024, and the related notes (collectively referred to as the "financial statements"). We also have audited the Company's internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America (“generally accepted accounting principles”). Also, in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control — Integrated Framework (2013) issued by COSO.

Basis for Opinions

The Company's management is responsible for these financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management's Annual Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on these financial statements and an opinion on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the US federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

Our audits of the financial statements included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures to respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

Definition and Limitations of Internal Control over Financial Reporting

A company's internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company's internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company's assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing separate opinions on the critical audit matter or on the accounts or disclosures to which it relates.

Revenue Recognition — Refer to Notes 1 and 17 to the financial statements

Critical Audit Matter Description

The Company recognizes revenue as it fulfills its performance obligations and transfers control of products to its customers. For products that have no alternative use and for which the Company has an enforceable right to payment (including a reasonable profit) throughout the production process, revenue is recognized over time. In general, revenue recognized over time primarily relates to the Company’s Aero/HS Products and Automotive Extrusions end markets, with the revenue for the remainder of its products recognized at a point in time. For contracts recognized over time, control transfer occurs incrementally during the Company’s production process as progress is made on fulfilling the performance obligation. The Company uses the input method of determining the progress, capturing direct costs beginning at the point that billet or cast ingot is introduced into production at either the extrusion phase or the rolling phase, respectively. For products in production, the Company recognizes revenue using the cost incurred to date plus an estimate of reasonable margin.

Contract assets primarily relate to the Company’s enforceable right to consideration for work completed but not billed at the reporting date on contracts for products recognized over time. Contract assets also include amounts related to the Company’s contractual right to consideration for finished goods recognized over time that were in transit as of period end.

Given the volume of contracts that are recognized over time and the complexity of the determination of over time revenue, we identified revenue for over time contracts as a critical audit matter.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to revenue recognized over time included the following, among others:

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We tested management’s controls over revenue recognized over time, including those over cost incurred to date and estimates of reasonable margin.

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We tested the mathematical accuracy of management’s calculation of revenue recognized over time and the related contract asset.

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We selected a sample of invoices with customers and performed the following:

o

We evaluated whether revenue was properly recognized as over time according to the contract terms with the customer.

o

We tested that the revenue associated with work-in-process and finished goods inventory was properly recognized at December 31, 2024.

/s/Deloitte & Touche LLP

Nashville, Tennessee

February 20, 2025

We have served as the Company's auditor since 2002.