CONSTELLIUM SE

NOTE 1 - BUSINESS AND SUMMARY OF ACCOUNTING POLICIES

Constellium is a global leader in the design and manufacture of a broad range of innovative specialty rolled and extruded aluminum products, serving a wide range of blue-chip customers primarily in the aerospace, packaging, automotive, commercial transportation, general industrial and defense end-markets. At September 30, 2025, the Group operated 24 manufacturing facilities,3 R&D centers and 3 administrative centers.

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.

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 September 30, 2025, results of operations and cash flows for the three-month and nine-month periods ended September 30, 2025 and 2024 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, 2024 ("the 2024 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 2025 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.

Revision of certain disclosures in previously issued financial statements

During the third quarter of 2025, the Group identified and corrected certain immaterial errors affecting metal price lag and the resulting Segment Adjusted EBITDA for the A&T segment for certain prior periods in 2025 and 2024. The errors resulted from misclassification of certain items within Cost of sales, which did not impact either the overall Cost of sales or the Group’s consolidated income statements but did impact the non-cash metal price lag and the resulting Segment Adjusted EBITDA for the A&T segment. The Group assessed the materiality of these errors on a quantitative and qualitative basis and concluded that the corrections were not material to any previously issued interim or annual consolidated financial statements. Accordingly, the affected prior period amounts presented in this filing, or that will be presented in prospective filings, have been revised. The impact of these revisions is presented below:

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Recently adopted and recently issued accounting guidance

In December 2023, the Financial Accounting Standards Board ("FASB") issued ASU 2023-09 -Improvements to Income Tax Disclosures. The standard requires disaggregated information about a reporting entity's effective tax rate reconciliation as well as information on income taxes paid. The standard is intended to benefit investors by providing more detailed income tax disclosures that would be useful in making capital allocation decisions and applies to all entities subject to income taxes. The new standard is effective for annual periods beginning after December 15, 2024. This accounting standard is effective for annual disclosures in fiscal year ended December 31, 2025. We are currently evaluating the impact of adoption on our annual financial disclosures.

In November 2024, the FASB issued ASU 2024-03 -Income Statement — Reporting Comprehensive Income — Expense Disaggregation Disclosures, requiring public business entities to disclose, on an annual and interim basis, disaggregated information about certain income statement line items in a tabular format in the notes to the financial statements. The standard is intended to benefit investors by providing more detailed expense information notably on employee compensation, depreciation and amortization and purchase of inventory, which is critical to understanding an entity’s performance, assessing its prospects for future cash flows and comparing its performance both over time and with that of other entities. This accounting standard as updated in ASU 2025-01 -Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Clarifying the Effective Date which clarified the interim reporting effective date of ASU 2024-03 is effective for annual periods beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The guidance may be applied prospectively or retrospectively. We are currently evaluating the impact of adoption on our financial disclosures.

The Group plans to adopt these new standards, amendments and interpretations 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.

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NOTE 2 - REVENUE

In the following table, revenue is disaggregated by product line. See Note 3 - Segment information herein for additional disclosures of revenue disaggregated by operating segments.

Revenue is recognized at a point in time, except for certain products with no alternative use for which we have a right to payment, which represent less than 1% of total revenue.

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NOTE 3 - SEGMENT INFORMATION

Constellium hasthree reportable business segments - Aerospace & Transportation ("A&T"), Packaging & Automotive Rolled Products ("P&ARP") and Automotive Structures & Industry ("AS&I") - and Holdings & Corporate ("H&C"). Holdings & Corporate (‘H&C’) includes certain costs of our corporate support functions and our technology centers.

3.1 Segment revenue, Segment costs and Segment Adjusted EBITDA

(A) Other segment expenses primarily include selling and general administrative expenses and research and development expenses.

3.2 Reconciliation of Segment Adjusted EBITDA to Net Income

Constellium’s chief operating decision-maker measures the profitability and financial performance of its operating segments based on Segment Adjusted EBITDA. Segment Adjusted EBITDA is defined as income / (loss) from continuing operations before income taxes, results from joint ventures, net finance costs, other expenses and depreciation, amortization as adjusted to exclude restructuring costs, impairment charges, unrealized gains or losses on derivatives and on foreign exchange differences on transactions that do not qualify for hedge accounting, metal price lag, share-based compensation expense, non- operating gains / (losses) on pension and other post-employment benefits, expenses on factoring arrangements, effects of certain purchase accounting adjustments, start-up and development costs or acquisition, integration and separation costs, certain incremental costs and other exceptional, unusual or generally non-recurring items.

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(A)Metal price lag represents the financial impact of the timing difference between when aluminum prices included within Constellium's Revenue are established and when aluminum purchase prices included in Cost of sales are established, which is a non-cash financial impact. The calculation of metal price lag adjustment is based on a standardized methodology applied at each of Constellium’s manufacturing sites. Metal price lag is calculated as the average value of product purchased in the period, approximated at the market price, less the value of product in inventory at the weighted average of metal purchased over time, multiplied by the quantity sold in the period.

(B)For the three and nine months ended September 30, 2024, impairment related to property, plant and equipment in our Valais (Switzerland) operations.

(C)For the nine months ended September 30, 2025, Other mainly includes $9 million of insurance proceeds and $8 million of clean-up costs related to the flooding of our facilities in Valais (Switzerland).

For the nine months ended September 30, 2024, Other mainly includes $6 million of inventory impairment as a result of the flooding of our facilities in Valais (Switzerland) as well as $4 million of costs associated with non-recurring corporate transformation projects, partially offset by a $2 million gain from the acquisition of the non-controlling interests of Railtech Alu-Singen.

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3.3 Segment capital expenditures

(A)Purchase of property plant and equipment, net of grants received and insurance compensation related to property plant and equipment.

3.4 Segment depreciation, amortization and impairment

3.5 Segment assets

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NOTE 4 - OTHER GAINS AND LOSSES - NET

(A)Realized and unrealized gains and losses are related to derivatives entered into with the purpose of mitigating exposure to volatility in foreign currencies and commodity prices and that do not qualify for hedge accounting.

(B)For the three and nine months ended September 30, 2024, impairment related to property, plant and equipment in our Valais (Switzerland) operations.

(C)For the three and nine months ended September 30, 2024, the losses resulting from flooding in Sierre and Chippis include clean-up costs and inventory impairment and are net of $22 million of insurance proceeds.

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NOTE 5 - FINANCE COSTS - NET

(A)For the three months ended September 30, 2025, and 2024, interest expense on borrowings included $23 million of interest expenses related to Constellium SE Senior Notes including amortization of debt issuance costs, in each period. For the nine months ended September 30, 2025, and 2024, interest expense on borrowings included $67 million and $66 million of interest expenses related to Constellium SE Senior Notes including amortization of debt issuance costs, respectively.

(B)In August 2024, Constellium SE redeemed its $250 million 5.875% Senior Notes due 2026 and €400 million 4.250% Senior Notes due 2026. The net loss on the settlement of debt included $3 million of write‐off of unamortized issuance costs related to the redemption of our Senior Notes that were due in 2026.

(C) The Group hedges the currency exposure when using external funding sources in a currency other than the functional currency of the entities being funded. Changes in the fair value of these hedging derivatives are recognized within Finance costs – net in the Interim Consolidated Income Statement.

(D) Borrowing costs directly attributable to the construction of assets are capitalized. The capitalization rate was 5% for the three and nine months ended September 30, 2025, and 2024.

NOTE 6 - INCOME TAX

Income tax expense for interim periods is recognized based on the annualized effective tax rate expected for the full year adjusted for the tax effect of certain items recognized in full in the interim period.

Our effective tax rate was 30.2% and 57.9% of our income before tax for the three months ended September 30, 2025 and 2024, respectively, and 33.8% and 29.9% of our income before tax for the nine months ended September 30, 2025, and 2024, respectively.

The effective tax rate for the three and nine months ended September 30, 2025 includes the impact of the temporary surtax in France, which was enacted in February 2025 and increased the 2025 statutory tax rate from 25.82% to an estimate of 29.52%. The difference between the effective tax rate and the statutory tax rate for the three and nine months ended September 30, 2025 was primarily due to the geographical mix of our pre-tax results and losses in certain jurisdictions where a full valuation allowance was recorded. There is no significant impact on the Company's financial statements for the three and nine months ended September 30, 2025 as a result of the One Big Beautiful Bill Act (the "OBBB Act").

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NOTE 7 - EARNINGS PER SHARE

Basic earnings per share are computed using the weighted-average number of ordinary shares outstanding during the period. Diluted earnings per share are computed using the weighted-average number of ordinary shares and ordinary share equivalents outstanding during the period. Ordinary share equivalents represent the dilutive effect of outstanding equity-based awards.

The reconciliation of the numerator and denominator of basic and diluted earnings per share was as follows:

For the three and nine months ended September 30, 2025, and 2024, no ordinary shares assuming exercise of equity-based awards were excluded from the computation of diluted earnings per share because the effect of their exercise would be anti-dilutive.

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NOTE 8 - TRADE RECEIVABLES AND OTHER

Factoring arrangements

The Group has entered into several accounts receivable factoring programs with selected financial institutions for certain receivables of the Group.

The proceeds from the sale of certain of these receivables comprise a combination of cash and a deferred purchase price receivable. The deferred purchase price receivable is ultimately realized by the Group following the collection by the financial institutions of the underlying receivables sold. The beginning deferred purchase price balance for nine months ended September 30, 2025 and 2024 was $2 million and $8 million, respectively. During each of the aforementioned periods, there were non-cash additions to the deferred purchase price receivable of $0 million and $65 million (these additions are excluded from the Interim Statement of Cash Flow as they are non-cash investing transactions), respectively, and cash collections of $2 million and $63 million, respectively. This activity resulted in an ending deferred purchase price receivable balance of $0 million and $10 million, for the nine months ended September 30, 2025 and 2024, respectively, recorded in Fair value of derivatives instruments and other financial assets in the consolidated balance sheets.

The Group has recorded $5 million and $6 million of expenses related to its factoring programs in the three months ended September 30, 2025 and 2024, respectively, and $16 million in both the nine months ended September 30, 2025 and 2024. These amounts are presented in Other gains and losses - net in its Interim Consolidated Income Statement.

NOTE 9 - INVENTORIES

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NOTE 10 - TRADE PAYABLES AND OTHER

Contract liabilities and other liabilities to customers

Revenue related to contract liabilities and other liabilities to customers for the nine months ended September 30, 2025 and 2024 are presented in the table below:

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NOTE 11 - DEBT

11.1 Analysis by nature

(A)Other loans include $23 million of financial liabilities relating to the sale and leaseback of assets that were considered to be financing arrangements in substance.

(B)Current portion of borrowings include mainly accrued interest and current portions of finance leases and other long-term loans relating to the sale and leaseback of assets.

The fair values of Constellium SE Senior Notes issued in June 2020, February 2021, June 2021 and August 2024 were 99.9%,95.2%,97.5% and 102.7%, respectively, of the nominal value and amounted to $325 million, $476 million, $343 million and $721 million, respectively, at September 30, 2025, compared to $319 million, $453 million, $297 million, and $658 million, respectively, at December 31, 2024.

The €100 million French Inventory Facility was amended in February 2025 and the maturity was extended to December 2027. The Facility remained undrawn at September 30, 2025.

The Group was in compliance with all applicable financial debt covenants at September 30, 2025 and December 31, 2024.

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NOTE 12 - FINANCIAL INSTRUMENTS

12.1 Fair values of financial instruments

All derivatives are presented at fair value in the Interim Consolidated Balance Sheets:

The fair values of trade receivables, other financial assets and liabilities approximate their carrying values, as a result of their liquidity or short maturity and the fair value of borrowings are disclosed in Note 11 - Debt.

12.2 Valuation hierarchy

The following table provides an analysis of financial instruments measured at fair value, grouped into levels based on the degree to which the fair value is observable:

•Level 1 is based on a quoted price (unadjusted) in active markets for identical financial instruments. Level 1 includes aluminum, copper and zinc futures that are traded on the LME.

•Level 2 is based on inputs other than quoted prices included within Level 1 that are observable for the assets or liabilities, either directly (i.e., prices), or indirectly (i.e., derived from prices). Level 2 includes foreign exchange derivatives, natural gas derivatives, silver derivatives and aluminum premium derivatives. The present value of future cash flows based on the forward or on the spot exchange rates at the balance sheet date is used to value foreign exchange derivatives.

•Level 3 is based on inputs for the asset or liability that are not based on observable market data (unobservable inputs). Trade receivables are classified as a Level 3 measurement under the fair value hierarchy.

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There was no material transfer of asset and liability categories into or out of Level 1, Level 2 or Level 3 during the nine months ended September 30, 2025, nor the year ended December 31, 2024.

12.3 Foreign exchange

Foreign exchange risk is the risk that the fair value or future cash flows of an exposure will fluctuate because of changes in foreign exchange rates.

Net assets, earnings and cash flows are influenced by multiple currencies due to the geographic diversity of sales and the countries in which the Group operates.

Constellium has the following foreign exchange risk: i) transaction exposures, which include commercial transactions related to forecasted sales and purchases and on-balance sheet receivables/payables resulting from such transactions and financing transactions related to external and internal net debt, and ii) translation exposures, which relate to net investments in foreign entities that are converted in U.S. dollar amounts in the Consolidated Financial Statements.

Foreign exchange impacts related to the translation of net investments in non-USD functional currency subsidiaries from functional currency to U.S. dollars, and of the related revenue and expenses, are not hedged as the Group operates in these various countries on a permanent basis except as described below.

i. Commercial transaction exposures

The Group policy is to hedge committed and highly probable forecasted foreign currency operational transactions. The Group uses foreign exchange forwards and foreign exchange swaps for this purpose.

The following tables outline the nominal value (converted to millions of U.S. Dollars at the closing rate) of forward derivatives for Constellium’s most significant foreign exchange exposures at September 30, 2025.

The Group has agreed to supply a major customer with fabricated metal products from an entity with Euro functional currency, while invoicing in U.S. Dollars. The Group has entered into significant foreign exchange derivatives that matched related highly probable future conversion sales. The Group designates a substantial portion of these derivatives for hedge accounting, with a total nominal amount of $312 million and $410 million at September 30, 2025 and December 31, 2024 respectively, with maturities ranging from 2025 to 2029. Changes in the fair value of cash flow hedges are reported by the

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Group as a component of Accumulated other comprehensive income, net of tax and reclassified into earnings when the forecasted transaction affects earnings.

The table below details the effect of foreign currency derivatives in the Interim Consolidated Income Statement, the Interim Consolidated Statement of Cash Flows and the Interim Consolidated Statement of Comprehensive Income:

(A)Commercial derivatives settled during the period are presented in net cash flows from operating activities in the Interim Consolidated Statement of Cash Flows.

(B)Gains or losses on the hedging instruments are expected to offset losses or gains on the underlying hedged forecasted sales that will be reflected in future years when these sales are recognized.

(C)Changes in fair value of derivatives that qualify for hedge accounting are included in revenue when the related customer invoices are issued.

ii. Financing transaction exposures

When the Group enters into intercompany loans and deposits, the financing is generally provided in the functional currency of the subsidiary. The foreign currency exposure of the Group’s external funding and liquid assets is systematically hedged either naturally through intercompany foreign currency loans and deposits or through foreign currency derivatives.

At September 30, 2025, the net hedged position related to long-term and short-term loans and deposits in U.S. dollars included a forward sale of $260 million versus the Euro using simple foreign exchange forward contracts.

(A)Net debt derivatives settled during the period are presented in Other financing activities in the Interim Consolidated Statement of Cash Flows.

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Total realized and unrealized gains or losses on debt derivatives are expected to partially offset the total realized and unrealized gains or losses on financing activities, both included in Finance costs - net.

12.4 Commodities

The Group is subject to the effects of market fluctuations in the price of aluminum, which is the Group’s primary metal input and a significant component of its output. The Group is also exposed to variation in regional premiums and to a lesser extent, in the price of zinc, natural gas, silver and copper, and other alloying metals.

The Group policy is to minimize exposure to aluminum price volatility by passing through the aluminum price risk to customers and using derivatives where necessary. For most of its aluminum price exposure, sales and purchases of aluminum are converted to be on the same floating basis and then the same quantities are bought and sold at the same market price.

Temporary increases in inventory, to the extent material, are sold forward to the expected sales date to ensure the price paid for the metal will be substantially redeemed when it is sold.

The Group also purchases copper, aluminum premium, silver and zinc derivatives to offset the commodity exposure where sales contracts have embedded fixed price agreements for these commodities.

In addition, the Group purchases natural gas fixed price derivatives to lock in energy costs where a fixed price purchase contract is not possible.

At September 30, 2025, the nominal amount of commodity derivatives is as follows:

The value of the contracts will fluctuate due to changes in market prices but our hedging strategy helps protect the Group’s margin on future conversion and fabrication activities. At September 30, 2025, these contracts were directly entered into with external counterparties.

The Group does not apply hedge accounting on commodity derivatives and therefore mark-to-market movements are recognized in Other gains and losses - net.

(A)Commodity derivatives settled during the period are presented in net cash flows from operating activities in the Interim Consolidated Statement of Cash Flows.

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NOTE 13 - PENSION AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS

NOTE 14 - PROVISIONS

Close down, environmental and remediation costs

Environmental remediation costs are accounted for based on the Group's best estimate of the costs of its environmental clean-up obligations. The Group also records provisions for close down and restoration efforts based on the net present value of estimated future costs of the dismantling and demolition of infrastructure and the removal of residual material of disturbed areas. These provisions are expected to be settled over the next 40 years depending on the nature of the disturbance and the technical remediation plans.

Contingencies

The Group is involved, and may become involved, in various lawsuits, claims and proceedings relating to customer claims, product liability, employee and retiree benefit matters and other commercial matters. The Group records provisions for pending litigation matters when it determines that it is probable that an outflow of resources will be required to settle the obligation, and such amounts can be reasonably estimated. In some proceedings, the issues raised are or can be highly complex and subject to significant uncertainties and amounts claimed are and can be substantial. As a result, the probability of loss and an estimation of damages are and can be difficult to ascertain.

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NOTE 15 - SHARE CAPITAL

Share capital amounted to €2,936,397.68 at September 30, 2025, divided into 146,819,884 ordinary shares, each with a nominal value of €0.02 and fully paid-up. All shares are of the same class and, except for treasury shares, have the right toone vote each.

(A)Includes 9,018,105 and 3,296,576 treasury shares at September 30, 2025 and December 31, 2024, respectively. The number of outstanding shares amounted to 137,801,779 and 143,523,308 at September 30, 2025 and December 31, 2024, respectively.

NOTE 16 - ACCUMULATED OTHER COMPREHENSIVE INCOME

The following tables summarize the change in the components of accumulated other comprehensive income / loss, excluding non-controlling interests, for the periods presented:

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NOTE 17 - SHARE-BASED COMPENSATION

Performance-Based Restricted Stock Units (equity-settled)

During the nine months ended September 30, 2025, the Company granted 1,154,859 Performance-Based Restricted Stock Units ("PSUs") to selected employees of the Group. The fair value of PSU awards with performance and service conditions is estimated using the value of Constellium SE’s ordinary shares on the date of grant. The fair value of PSU awards with market conditions is estimated using a Monte Carlo simulation model on the date of grant.

These units vest if the following conditions are met:

•A vesting condition under which the beneficiaries must be continuously at the service of the Company through the end of athree-year vesting period; and

•A performance condition, contingent on the TSR performance of Constellium shares over the vesting period compared to the TSR of specified indices. PSUs will ultimately vest based on a vesting multiplier which ranges from 0% to 200%.

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The following table lists the inputs to the valuation model used for the PSUs granted during the nine months ended September 30, 2025:

(A)Volatility in the share prices of the Company and companies included in indices were estimated based on observed historical volatilities over a period equal to the PSU vesting period.

Restricted Stock Units Award Agreements (equity-settled)

During the nine months ended September 30, 2025, the Company granted 1,026,520 Restricted Stock Units (RSUs) to selected employees of the Group subject to the beneficiaries remaining continuously employed by or at the service of the Group from the grant date to the end of thethree-year vesting period. The fair value of the RSUs awarded is $11.90, being the quoted market price at grant date.

Expense recognized during the period

Total share-based compensation expense was $20 million and $18 million for the nine months ended September 30, 2025 and 2024, respectively and $7 million and $5 million for the three months ended September 30, 2025 and 2024.

At September 30, 2025, unrecognized compensation expense related to the RSUs was $18 million, which will be recognized over the remaining weighted average vesting period of 2.0 years, and unrecognized compensation expense related to the PSUs was $29 million, which will be recognized over the remaining weighted average vesting period of 2.0 years.

Vested plan during the period

Fair values of vested RSUs and PSUs amounted to $24 million for nine months ended September 30, 2025. They are excluded from the Statement of Cash flows as non-cash financing activities.

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