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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

_______________________________________________________________________

 FORM 10-K/A

(Amendment No. 1)

_______________________________________________________________________

☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the fiscal year ended December 31, 2023

or

☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from _______ to _______

Commission File Number 001-38694

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ARCADIUM LITHIUM PLC

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Bailiwick of Jersey	98-1737136
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
Suite 12, Gateway Hub
Shannon Airport House
Shannon, Co. Clare
Ireland	V14 E370
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: 353-1-6875238

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Securities registered pursuant to Section 12(b) of the Act: 

Title of each class	Trading Symbol (s)	Name of each exchange on which registered
Ordinary Shares, $1.00 par value per share	ALTM	New York Stock Exchange

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  ☒    No  ☐  

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.   Yes ☐    No  ☒

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.   Yes ☒    No  ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).  Yes  ☒    No  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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Large accelerated filer	☒	Accelerated filer	☐
Non-accelerated filer	¨	Smaller reporting company	☐
		Emerging growth company	☐
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.			☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. Yes  ☒    No  ☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ¨

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act).   Yes  ☐    No  ☒

The aggregate market value of voting stock held by non-affiliates of the registrant as of June 30, 2023, the last day of the registrant’s second fiscal quarter, was $4,896,548,501. The market value of voting stock held by non-affiliates excludes the value of those shares held by executive officers and directors of the registrant.

Indicate the number of shares outstanding of each of the registrant’s classes of common stock, as of the latest practicable date.

Class	January 31, 2024
Ordinary Shares, par value $1.00 per share	1,074,397,786

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant's definitive proxy statement to be filed with the Securities and Exchange Commission in connection with the registrant's annual meeting of shareholders or on an amendment on Form 10-K/A are incorporated by reference in Part III.

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EXPLANATORY NOTE

Arcadium Lithium plc (the "Company") is filing this Amendment No. 1 on Form 10-K/A ("Amended 10-K") to its Annual Report on Form 10-K for the year ended December 31, 2023 ("Original 10-K") filed with the U.S. Securities and Exchange Commission ("SEC") on February 29, 2024 to include the annual financial statements and related notes of Nemaska Lithium, Inc. ("NLI") as at and for the fiscal year ended December 31, 2022, an unconsolidated joint venture as of December 31, 2022, in which we currently have a 50% ownership interest.

On October 18, 2023, we entered into an amendment to our shareholders agreement with NLI, and also amendments to certain related service agreements. The amendments to these agreements provide our subsidiary Québec Lithium Partners (UK) Limited ("QLP") with control of substantive participating rights, and as such, the Company began to consolidate NLI as of October 18, 2023. Nemaska Lithium, in which we continue to own a 50% equity interest, was previously accounted for using the equity method. Rule 3-09 of Regulation S-X under the Securities Exchange Act of 1934, as amended, provides that if a 50 percent-or-less-owned person accounted for by the equity method meets the first or third condition of the significant subsidiary tests set forth in Rule 1-02(w) of Regulation S-X, substituting 20 percent for 10 percent, separate financial statements for such 50 percent-or-less-owned person shall be filed. NLI met the significant subsidiary test described above for fiscal year ended December 31, 2022. The Original 10-K is being amended by this Amended 10-K to include as exhibits: (i) the NLI audited financial statements for fiscal year ended December 31, 2022 and unaudited financial statements for the fiscal year ended December 31, 2021, each prepared in accordance with generally accepted accounting principles in the United States; (ii) the consent of the independent auditor of NLI; and (iii) certifications by our Chief Executive Officer and Chief Financial Officer. This Amended 10-K does not otherwise update any exhibits as originally filed and does not otherwise reflect events that occurred after the filing date of the Original 10-K.

PART IV

ITEM 15.    EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

(a)Exhibits

Exhibit No.	Exhibit Description
23.1	Consent of KPMG LLP
31.3	Certifying Statement of the Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31.4	Certifying Statement of the Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
99.1	Financial Statements of Nemaska Lithium, Inc. for the year ended December 31, 2022
101	Interactive Data File
104	Cover Page Interactive Data File

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

ARCADIUM LITHIUM PLC (Registrant)
By:	/S/ GILBERTO ANTONIAZZI
	Gilberto Antoniazzi, Vice President and Chief Financial Officer

Date: April 1, 2024