System1 CPO RSU vesting prompts tax share withholding

System1, Inc. Chief People Officer Elizabeth Sestanovich reported a routine tax-related share disposition tied to restricted stock units.

Rhea-AI Filing Summary

System1, Inc. Chief People Officer Elizabeth Sestanovich reported a routine tax-related share disposition tied to restricted stock units. When 670 RSUs vested, the company withheld 341 shares of Class A Common Stock at $2.26 per share to cover tax obligations, rather than selling shares on the open market.

After this withholding, Sestanovich directly holds 58,948 shares of Class A Common Stock, including 42,010 unvested RSUs. This event reflects standard equity compensation and tax withholding mechanics, not a discretionary buy or sell decision.

Insider Trade Summary

Exercise Price or Tax Liability: 341 shares

Exercise Price or Tax Liability 1 txn

Insider Sestanovich Elizabeth

Role Chief People Officer

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Class A Common Stock	341	$2.26	$770.66

Holdings After Transaction: Class A Common Stock — 58,948 shares (Direct)

Footnotes (2)

1. F1. Upon the vesting of 670 restricted stock units ("RSUs") previously granted to the reporting person, the Company withheld 341 shares to cover the reporting person's tax withholding obligation with respect to the vesting of such RSUs.
2. F2. Includes 42,010 unvested RSUs.

Key Figures

Shares withheld for taxes: 341 shares Price per withheld share: $2.26 per share Shares after transaction: 58,948 shares +2 more

5 metrics

Shares withheld for taxes 341 shares Withheld upon RSU vesting to cover tax obligation

Price per withheld share $2.26 per share Value used for tax-withholding disposition

Shares after transaction 58,948 shares Direct Class A Common Stock holdings following transaction

RSUs vested 670 RSUs Restricted stock units that vested and triggered withholding

Unvested RSUs 42,010 RSUs Unvested restricted stock units included in holdings

Key Terms

restricted stock units ("RSUs"), tax withholding obligation, unvested RSUs, tax-withholding disposition

4 terms

restricted stock units ("RSUs") financial

"Upon the vesting of 670 restricted stock units ("RSUs") previously granted to the reporting person..."

Restricted stock units (RSUs) are a company promise to give an employee shares of stock (or cash equivalent) in the future, but only after certain conditions—usually staying with the company for a set time or hitting performance goals—are met. Investors watch RSUs because when they vest they increase the number of shares outstanding and can lead insiders to sell shares, affecting share price, company dilution and the true cost of employee pay.

tax withholding obligation financial

"the Company withheld 341 shares to cover the reporting person's tax withholding obligation with respect to the vesting..."

unvested RSUs financial

"Includes 42,010 unvested RSUs."

tax-withholding disposition financial

"transaction_action": "tax-withholding disposition""

A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did System1 (SST) Chief People Officer report in this Form 4?

Elizabeth Sestanovich reported a tax-withholding disposition of shares tied to RSU vesting. When 670 RSUs vested, the company withheld 341 shares to satisfy tax obligations, a routine compensation-related event rather than an open-market stock sale.

How many System1 (SST) shares were withheld for taxes in this filing?

The company withheld 341 shares of Class A Common Stock at $2.26 per share. These shares covered Elizabeth Sestanovich’s tax withholding obligation arising from the vesting of 670 restricted stock units, as is common with equity-based compensation.

Does this System1 (SST) Form 4 show an open-market sale by the executive?

No, the Form 4 shows a tax-withholding disposition, not an open-market sale. Shares were withheld by the company to pay taxes on RSU vesting, meaning there was no discretionary trade executed by the executive in the market.

What are Elizabeth Sestanovich’s holdings in System1 (SST) after this transaction?

Following the transaction, Elizabeth Sestanovich directly holds 58,948 shares of Class A Common Stock. This amount includes 42,010 unvested RSUs, indicating a significant ongoing equity-based compensation position aligned with the company’s performance.

What triggered the tax-withholding transaction reported for System1 (SST)?

The transaction was triggered when 670 RSUs vested for Elizabeth Sestanovich. To cover the resulting tax withholding obligation, the company retained 341 shares rather than delivering them, a standard mechanism for handling taxes on vested equity awards.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/17/2026 - 08:32 PM Learn about SEC filing dates

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Sestanovich Elizabeth

(Last) (First) (Middle)

4235 REDWOOD AVE

(Street)

LOS ANGELES CALIFORNIA 90066

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
System1, Inc. [ SST ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/15/2026

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

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

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

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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
Class A Common Stock	04/15/2026		F		341(1)	D	$2.26	58,948(2)	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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. Upon the vesting of 670 restricted stock units ("RSUs") previously granted to the reporting person, the Company withheld 341 shares to cover the reporting person's tax withholding obligation with respect to the vesting of such RSUs.

2. Includes 42,010 unvested RSUs.

Remarks:

	/s/ Daniel Weinrot, Attorney-in-Fact for Elizabeth Sestanovich	04/17/2026
	** 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 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).
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 4: SEC 1474 (03-26)