CENTURY ALUMINUM CO 10-Q

Item 4. Controls and Procedures Evaluation of Disclosure Controls and Procedures As of September 30, 2025, 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 not effective as of September 30, 2025. Previously Reported Material Weaknesses in Internal Control over Financial Reporting Management is responsible for establishing and maintaining adequate internal control over financial reporting as defined in Exchange Act Rule 13a-15(f) and 15d-15(f) based on the criteria established in Internal Control-Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission ("the COSO Framework"). As reported in our Form 10-K for the fiscal year ended December 31, 2024, we did not maintain effective internal control over financial reporting as of December 31, 2024 as a result of material weaknesses in general information technology controls and business process controls at Jamalco. A material weakness (as defined in Rule 12b-2 under the Exchange Act) is a deficiency, or combination of deficiencies, in internal control over financial reporting such that there is a reasonable possibility that a material misstatement of our annual or interim financial statements will not be prevented or detected on a timely basis. Refer to our 2024 Form 10-K for a description of our material weaknesses. Ongoing Remediation Efforts to Address Material Weaknesses Our material weaknesses were not remediated as of September 30, 2025. Management is committed to maintaining a strong internal control environment. Management has begun to implement measures designed to ensure that previously identified 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, our remediation efforts involve implementing additional controls to address the completeness and accuracy of information utilized in business process controls. We intend to remediate the material weaknesses as soon as possible; however, the material weaknesses will not be considered remediated until the applicable controls operate for a sufficient period of time and management has concluded, through testing, that the appropriate controls are operating effectively. Changes in Internal Control over Financial Reporting Other than the changes associated with the material weaknesses and remediation actions noted above, there have been no changes in our internal control over financial reporting during the three months ended September 30, 2025 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting. 37 Table of Contents PART II – OTHER INFORMATION