Sec Form 3 Filing - SOFTBANK GROUP CORP. @ ARM HOLDINGS PLC /UK - 2026-03-18

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person SOFTBANK GROUP CORP. 2. Issuer Name and Ticker or Trading Symbol ARM HOLDINGS PLC /UK [ ARM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 1-7-1 KAIGAN, MINATO-KU 3. Date of Earliest Transaction (MM/DD/YY) 03/18/2026 (Street) TOKYO105-7537 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Ordinary Shares ( 1 ) 922,733,999 I By limited liability company ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other SOFTBANK GROUP CORP. 1-7-1 KAIGAN MINATO-KU TOKYO105-7537 X X Signatures SoftBank Group Corp., By: /s/ Yuko Yamamoto, Head of Corporate Legal Department 03/18/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The ordinary shares, nominal value 0.001 GBP per share ("Ordinary Shares"), of Arm Holdings plc (the "Company") may be represented by American Depositary Shares, each representing one Ordinary Share. ( 2 )Represents shares held of record by Kronos II LLC ("Kronos II"). Kronos II is an indirect wholly-owned subsidiary of SoftBank Group Corp. ("SoftBank Group"). Kronos II is a direct wholly-owned subsidiary of Kronos I (UK) Limited, which is in turn a direct wholly-owned subsidiary of Kronos Holdco (UK) Limited, which is in turn a direct wholly-owned subsidiary of SoftBank Group Capital ("SBGC"). SBGC is an indirect wholly-owned subsidiary of SoftBank Group, whose interests are held 46% by SoftBank Group and 54% by SoftBank Group Overseas GK, a direct wholly-owned subsidiary of SoftBank Group.

Remarks: Solely for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, SoftBank Group may be deemed a "director by deputization" by virtue of its director appointment rights pursuant to that certain Shareholder Governance Agreement, dated September 19, 2023, by and between SoftBank Group and the Company.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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