CENTURY ALUMINUM CO

a. Evaluation of Disclosure Controls and Procedures

As of March 31, 2024, we carried out an evaluation, under the supervision and with the participation of our management, including our Chief Executive Officer and Principal Financial Officer, of the effectiveness of our disclosure controls and procedures. Based upon that evaluation, our management, including the Chief Executive Officer and Principal Financial Officer, concluded that our disclosure controls and procedures were effective as of March 31, 2024.

Material Weakness Remediation

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.

Our management is committed to maintaining a strong internal control environment. 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 have 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.

b. Changes in Internal Control over Financial Reporting

As permitted by applicable SEC guidance, we exclude General Alumina Holdings Limited, the holder of a 55% interest in our Jamalco joint venture ("Jamalco"), which was acquired on May 2, 2023, from our assessment of internal control over financial reporting and procedures for the first year after acquisition. However, we are in the process of extending our oversight and monitoring processes that support our internal control over financial reporting and disclosure controls and procedures to include Jamalco's operations. Except as described in the preceding sentence and above under "Material Weakness Remediation", during the three months ended March 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.