Sec Form 3 Filing - Bartels Laura Kathleen @ 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 Bartels Laura Kathleen 2. Issuer Name and Ticker or Trading Symbol ARM HOLDINGS PLC /UK [ ARM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Accounting Officer (Last) (First) (Middle) C/O ARM HOLDINGS PLC, 110 FULBOURN ROAD 3. Date of Earliest Transaction (MM/DD/YY) 03/18/2026 (Street) CAMBRIDGECB1 9NJ 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 ) 20,066 D

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 Restricted Stock Units ( 3 ) ( 2 ) ( 2 ) Ordinary Shares ( 1 ) 12,592 D Restricted Stock Units ( 3 ) ( 4 ) ( 4 ) Ordinary Shares ( 1 ) 6,895 D Restricted Stock Units ( 3 ) ( 5 ) ( 5 ) Ordinary Shares ( 1 ) 2,308 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Bartels Laura Kathleen C/O ARM HOLDINGS PLC 110 FULBOURN ROAD CAMBRIDGECB1 9NJ Chief Accounting Officer Signatures /s/ George Kanelos, as Attorney-in-Fact for Laura Kathleen Bartels 03/18/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Ordinary shares, nominal value 0.001 GBP per share ("Ordinary Shares"), are held in the form of American Depositary Shares ("ADSs"). Each ADS represents 1 Ordinary Share. ( 2 )This restricted stock unit ("RSU") award was granted on May 1, 2025, 28.5% of which will vest on May 15, 2026, with quarterly vesting of 6.5% thereafter with 100% of the award fully vested on February 15, 2029. ( 3 )Each RSU represents the right to receive, following vesting, 1 Ordinary Share held in the form of an ADS. ( 4 )This RSU award was granted on May 13, 2024, 28.5% of which vested on May 15, 2025, with quarterly vesting of 6.5% thereafter with 100% of the award fully vested on February 15, 2028. The number in the table represents the total remaining unvested RSUs as of March 18, 2025. ( 5 )This RSU award was granted on May 22, 2023, 28.5% of which vested on May 15, 2024, with quarterly vesting of 6.5% thereafter with 100% of the award fully vested on May 15, 2026. The number in the table represents the total remaining unvested RSUs as of March 18, 2025.

Remarks: Exhibit 24 - Power of Attorney

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

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