[Form 3] ARM HOLDINGS PLC /UK Initial Statement of Beneficial Ownership

Rhea-AI Filing Summary

Arm Holdings plc director Karen E. Dykstra filed an initial statement of beneficial ownership, reporting both ordinary shares and restricted stock units. She holds 13,002 Ordinary Shares directly and an additional 707 Ordinary Shares indirectly through her spouse. She also reports two blocks of restricted stock units (RSUs) that each convert into ordinary shares held as American Depositary Shares (ADSs), with 2,130 underlying Ordinary Shares in one award and 2,141 underlying Ordinary Shares in another. One RSU grant vested in full on May 15, 2025, while the ADS delivery is deferred until she leaves the Board, and the other is scheduled to vest on May 15, 2026 with delivery likewise deferred until her Board service ends. Each ADS represents one Ordinary Share.

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

DYKSTRA KAREN E

(Last) (First) (Middle)

C/O ARM HOLDINGS PLC

110 FULBOURN ROAD

(Street)

CAMBRIDGE CB1 9NJ

(City) (State) (Zip)

UNITED STATES

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
03/18/2026

3. Issuer Name and Ticker or Trading Symbol
ARM HOLDINGS PLC /UK [ ARM ]

3a. Foreign Trading Symbol

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Ordinary Shares(1)	13,002	D
Ordinary Shares(1)	707	I	By Spouse

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Units	(2)	(2)	Ordinary Shares(1)	2,130	(3)	D
Restricted Stock Units	(4)	(4)	Ordinary Shares(1)	2,141	(3)	D

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. The restricted stock units ("RSUs") vested in full on May 15, 2025, but the ADSs have not been delivered pursuant to Ms. Dykstra's election to defer delivery until the date of termination of her service on the Board of Directors.

3. Each RSU represents the right to receive, following vesting, 1 Ordinary Share held in the form of an ADS.

4. The RSUs will vest in full on May 15, 2026, subject to continued service to Arm Holdings plc, but the ADSs will not be delivered until the date of termination of Ms. Dykstra's service on the Board of Directors pursuant to her election to defer such delivery.

Remarks:

Exhibit 24 - Power of Attorney

	/s/ George Kanelos, as Attorney-in-Fact for Karen E. Dykstra	03/18/2026
	** Signature of Reporting Person	Date
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 5 (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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 3: SEC 1473 (03-26)

FAQ

What does Karen E. Dykstra’s Form 3 for ARM show about her share ownership?

The Form 3 shows Karen E. Dykstra holds 13,002 Ordinary Shares directly and 707 Ordinary Shares indirectly through her spouse. She also reports restricted stock units tied to additional ordinary shares held as American Depositary Shares, reflecting her equity-based alignment with Arm Holdings plc.

How many restricted stock units does Karen E. Dykstra report in ARM’s Form 3?

Karen E. Dykstra reports two RSU awards covering 2,130 and 2,141 underlying Ordinary Shares. Each RSU converts into one Ordinary Share held as an American Depositary Share, giving her future rights to additional equity subject to vesting and delivery conditions.

When do Karen E. Dykstra’s ARM restricted stock units vest and get delivered?

One RSU grant vested fully on May 15, 2025, and another will vest on May 15, 2026, subject to continued service. However, delivery of the related ADSs is deferred until she terminates service on Arm Holdings plc’s Board of Directors, based on her election.

How are Arm Holdings plc Ordinary Shares represented in Karen E. Dykstra’s holdings?

Arm Holdings plc Ordinary Shares are held in the form of American Depositary Shares, with each ADS representing one Ordinary Share. Karen E. Dykstra’s reported RSUs entitle her to receive Ordinary Shares in ADS form once vested and delivered under the deferral terms she elected.

What indirect ownership does Karen E. Dykstra report in ARM stock?

She reports 707 Ordinary Shares held indirectly, noted as owned "By Spouse". This indicates an indirect beneficial interest through her spouse, in addition to her direct holdings and restricted stock units, as part of her overall reported equity position in Arm Holdings plc.