BUSINESS AND SUMMARY OF ACCOUNTING POLICIES	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
BUSINESS AND SUMMARY OF ACCOUNTING POLICIES	NOTE 1 - BUSINESS AND SUMMARY OF ACCOUNTING POLICIES Constellium is a global leader in the development, manufacture and sale of a broad range of high value-added specialty rolled and extruded aluminum products to the aerospace, space, defense, packaging, automotive, commercial transportation and general industrial end-markets. At June 30, 2026, the Group operated 23 manufacturing facilities, 3 R&D centers and 3 administrative centers. The Group has approximately 11,500 employees. Unless the context indicates otherwise, when we refer to “we,” “our,” “us,” “Constellium,” the “Group” and the “Company” in this document, we are referring to Constellium SE and its subsidiaries, and when we refer to “Constellium SE”, we are referring to Constellium SE on a standalone basis. Basis of presentation and principles of consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of Constellium SE and its controlled subsidiaries. All intercompany transactions and balances are eliminated. The accompanying unaudited interim condensed consolidated financial statements have been prepared by Constellium in accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the Securities and Exchange Commission (“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 statement of its financial position at June 30, 2026, results of operations and cash flows for the three-month and six-month periods ended June 30, 2026 and 2025 have been included. The accompanying unaudited interim condensed consolidated financial statements should be read in conjunction with the Group’s audited consolidated financial statements and accompanying notes in its Annual Report on Form 10-K for the year ended December 31, 2025 (“Annual Report”). 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. Use of estimates and assumptions The preparation of the Group’s consolidated financial statements in accordance with U.S. GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and the accompanying disclosures, and the disclosure of contingent liabilities. The principal areas of judgment relate to: (1) impairment of assets; (2) actuarial assumptions related to pension and other postretirement benefit plans; (3) tax uncertainties and valuation allowances; and (4) assessment of loss contingencies, including environmental and litigation liabilities. These judgments, estimates and assumptions are based on management’s best knowledge of the relevant facts and circumstances, giving consideration to previous experience. Future events and their effects cannot be predicted with certainty, and, accordingly, our accounting estimates require the exercise of judgment. The accounting estimates used in the preparation of our consolidated financial statements may change as new events occur, more experience is acquired, additional information is obtained, and our operating environment changes. The Group continuously reviews its significant assumptions and estimates in light of the uncertainty associated with the global geopolitical and macroeconomic conditions and their potential direct and indirect impacts on its business and its financial statements. There can be no guarantee that our assumptions will materialize or that actual results will not differ materially from estimates. Recently adopted and recently issued accounting guidance In May 2026, the Financial Accounting Standards Board (“FASB”) issued ASU 2026-02 Environmental Credits and Environmental Credit Obligations (Topic 818) which establishes requirements on how to recognize, measure, present and disclose environmental credits and environmental credit obligations. The guidance applies to all entities that buy, receive or internally generate environmental credits they intend to sell, trade or distribute. It also applies to entities that use such credits for compliance or voluntary purposes (e.g., for use in carbon-neutral or net-zero initiatives). The standard is effective for interim periods within fiscal years beginning after December 15, 2027. The guidance must be applied retrospectively by recognizing a cumulative effect adjustment to retained earnings at the date of initial application. Early adoption is permitted. The Group plans to adopt these and new standards, amendments and interpretations, as disclosed in our Annual Report, on their required effective dates and does not expect any material impact on its financial position, results of operations and cash flows as a result of their adoption.

BUSINESS AND SUMMARY OF ACCOUNTING POLICIES

6 Months Ended

Jun. 30, 2026

BUSINESS AND SUMMARY OF ACCOUNTING POLICIES

NOTE 1 - BUSINESS AND SUMMARY OF ACCOUNTING POLICIES

Constellium is a global leader in the development, manufacture and sale of a broad range of high value-added specialty

rolled and extruded aluminum products to the aerospace, space, defense, packaging, automotive, commercial transportation and

general industrial end-markets. At June 30, 2026, the Group operated 23 manufacturing facilities, 3 R&D centers and 3

administrative centers. The Group has approximately 11,500 employees.

Unless the context indicates otherwise, when we refer to “we,” “our,” “us,” “Constellium,” the “Group” and the

“Company” in this document, we are referring to Constellium SE and its subsidiaries, and when we refer to “Constellium SE”,

we are referring to Constellium SE on a standalone basis.

Basis of presentation and principles of consolidation

The accompanying unaudited interim condensed consolidated financial statements include the accounts of

Constellium SE and its controlled subsidiaries. All intercompany transactions and balances are eliminated.

The accompanying unaudited interim condensed consolidated financial statements have been prepared by Constellium in

accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the Securities and

Exchange Commission (“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 statement of its financial position at June 30, 2026, results of operations

and cash flows for the three-month and six-month periods ended June 30, 2026 and 2025 have been included. The

accompanying unaudited interim condensed consolidated financial statements should be read in conjunction with the Group’s

audited consolidated financial statements and accompanying notes in its Annual Report on Form 10-K for the year ended

December 31, 2025 (“Annual Report”). 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.

Use of estimates and assumptions

The preparation of the Group’s consolidated financial statements in accordance with U.S. GAAP requires management to

make judgments, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and

the accompanying disclosures, and the disclosure of contingent liabilities. The principal areas of judgment relate to:

(1) impairment of assets; (2) actuarial assumptions related to pension and other postretirement benefit plans; (3) tax

uncertainties and valuation allowances; and (4) assessment of loss contingencies, including environmental and litigation

liabilities. These judgments, estimates and assumptions are based on management’s best knowledge of the relevant facts and

circumstances, giving consideration to previous experience. Future events and their effects cannot be predicted with certainty,

and, accordingly, our accounting estimates require the exercise of judgment. The accounting estimates used in the preparation

of our consolidated financial statements may change as new events occur, more experience is acquired, additional information

is obtained, and our operating environment changes. The Group continuously reviews its significant assumptions and estimates

in light of the uncertainty associated with the global geopolitical and macroeconomic conditions and their potential direct and

indirect impacts on its business and its financial statements. There can be no guarantee that our assumptions will materialize or

that actual results will not differ materially from estimates.

Recently adopted and recently issued accounting guidance

In May 2026, the Financial Accounting Standards Board (“FASB”) issued ASU 2026-02 Environmental Credits and

Environmental Credit Obligations (Topic 818) which establishes requirements on how to recognize, measure, present and

disclose environmental credits and environmental credit obligations. The guidance applies to all entities that buy, receive or

internally generate environmental credits they intend to sell, trade or distribute. It also applies to entities that use such credits

for compliance or voluntary purposes (e.g., for use in carbon-neutral or net-zero initiatives). The standard is effective for

interim periods within fiscal years beginning after December 15, 2027. The guidance must be applied retrospectively by

recognizing a cumulative effect adjustment to retained earnings at the date of initial application. Early adoption is permitted.

The Group plans to adopt these and new standards, amendments and interpretations, as disclosed in our Annual Report,

on their required effective dates and does not expect any material impact on its financial position, results of operations and cash

flows as a result of their adoption.