CENTURY ALUMINUM CO

Evaluation of Disclosure Controls and Procedures

As of December 31, 2024, we carried out an evaluation, under the supervision and with the participation of our management, including our Chief Executive Officer and Chief Financial Officer, of the effectiveness of our disclosure controls and procedures. Based upon that evaluation, our management, including the Chief Executive Officer and Chief Financial Officer, concluded that our disclosure controls and procedures were ineffective as of December 31, 2024, because of material weaknesses in internal controls over financial reporting described in Management’s Report on Internal Control Over Financial Reporting below.

Management's Report on Internal Control over Financial Reporting

Management is responsible for establishing and maintaining an adequate system of internal control over financial reporting for the Company. This system is 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. Because of its inherent limitations, a system of internal control over financial reporting can provide only reasonable assurance and may not prevent or detect misstatements. Further, because of changes in conditions, effectiveness of internal control over financial reporting may vary over time. Our system of internal control contains self-monitoring mechanisms, and actions are taken to correct deficiencies as they are identified.

As required by Section 404 of the Sarbanes-Oxley Act, management conducted an evaluation of the effectiveness of the system of internal control over financial reporting for the year ended December 31, 2024. Management’s evaluation was based on the framework in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations (COSO) of the Treadway Commission. Based on this evaluation, management concluded that our system of internal control over financial reporting was not effective as of December 31, 2024 due to the material weaknesses described below.

1 - The Company failed to design and implement appropriate information technology general controls in the areas of logical access controls including provisioning, deprovisioning, privileged access, user access review, application changes and monitoring related to Jamalco.

2 - The Company failed to design and implement appropriate business process level controls, including controls to address the completeness and accuracy of information derived from its affected information technology systems at Jamalco, which resulted in a material weakness related to reconciliation controls and insufficient review controls related to inventories, accounts payable, accrued expenses, cost of goods sold and property, plant, and equipment.

Notwithstanding the material weaknesses, management believes the consolidated financial statements included in this Annual Report on Form 10-K present fairly, in all material respects, the Company’s financial condition, results of operations and cash flows as of and for the periods presented in accordance with U.S. GAAP.

The effectiveness of our internal control over financial reporting has been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their report which appears in Part II, Item 8 of this Annual Report on Form 10-K.

Remediation Plan for Material Weaknesses

Management plans to implement measures designed to ensure that the control deficiencies contributing to the material weaknesses are remediated, such that these controls are designed, implemented, and operating effectively. The remediation actions for general information technology controls include:(i) designing and implementing controls related to deprovisioning, privileged access, and user access reviews, (ii) developing an enhanced risk assessment process to evaluate and monitor system changes, and (iii) providing training associated with control design and execution.

The remediation actions for business process controls include: (i) designing and implementing controls related to account reconciliations (ii) improving the accuracy of supporting schedules underlying transactions, and (iii) timely capitalization of fixed assets. Additionally, we expect our remediation efforts to involve implementing additional controls to address the completeness and accuracy of information utilized in business process controls.

We believe that these actions will remediate the material weaknesses. The material weaknesses will not be considered remediated, however, until the applicable controls operate for a sufficient period of time and management has concluded, through testing, that these controls are operating effectively.

Previously Reported Material Weakness

As of December 31, 2023, our management had identified a deficiency in the design of internal control over financial reporting related to the application of purchase accounting to our acquisition of Jamalco. The design deficiency was determined to be a material weakness related to the review of the Company's allocation of excess fair value acquired between non-controlling interest and preliminary deferred bargain purchase gain. In response to the identified material weakness above, during the three months ended March 31, 2024, management, with the oversight of the Audit Committee of the Board of Directors, took actions to remediate the material weakness in internal control over financial reporting in the first quarter of 2024. We changed the design of our internal controls over financial reporting to include a review of the allocation of the excess fair value of the net assets acquired at an entity level. We completed our assessment of the redesigned control related to the application of purchase accounting to determine if it was designed and operating effectively for all adjustments made during the three months ended March 31, 2024 in finalizing our purchase accounting. As a result of our assessment, management concluded that the material weakness associated with the application of purchase accounting was remediated as of March 31, 2024.

Changes in Internal Control over Financial Reporting

On May 2, 2023, our wholly-owned subsidiary, Century Aluminum Jamaica Holdings, Inc., completed the acquisition of all the outstanding share capital of General Alumina Holdings Limited, the holder of a 55% interest in Jamalco JV ("Jamalco"), an unincorporated joint venture engaged in bauxite mining and alumina production in Jamaica. Except for the remediation efforts related to the previous material weakness referred to above, during the year ended December 31, 2024, there were no changes in our internal control over financial reporting that materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.