[Form 4] Hyliion Holdings Corp. Insider Trading Activity

Rhea-AI Filing Summary

Joshua T. Mook, Chief Technology Officer of Hyliion Holdings Corp. (HYLN), reported a sale of company common stock on 08/25/2025. The filing discloses disposition of 8,430 shares at a reported price of $1.77 per share to satisfy a tax liability arising from the vesting and distribution of restricted stock units. After the sale, Mr. Mook beneficially owns 521,049 shares, held directly. The Form 4 is filed by one reporting person and is signed by Mr. Mook.

Positive

• Disclosed purpose: The filing explicitly states the sale was to pay a tax liability related to RSU vesting, clarifying the reason for the transaction.
• Substantial remaining ownership: The reporting person continues to beneficially own 521,049 shares, indicating ongoing insider alignment with shareholders.

Negative

• Insider sale: 8,430 shares were disposed of, which is a reduction in the reporting person's direct holdings.
• Sale price disclosed: The disposition occurred at $1.77 per share, representing the realized price for the sold shares.

Insights

Financial Analyst

TL;DR: Insider sold a small block of shares to cover RSU tax withholding; remaining stake is substantial at 521,049 shares.

The transaction is a routine post-vesting sale to satisfy tax obligations rather than an open-market investment decision. The sold amount, 8,430 shares at $1.77, represents a small fraction of the reported beneficial ownership. For investors, this filing documents insider activity and confirms the CTO retains a meaningful direct stake of 521,049 shares, which maintains alignment with shareholder interests.

Corporate Governance Expert

TL;DR: This Form 4 reflects a standard tax-related disposition following RSU vesting and carries no disclosed governance concerns.

The explanatory note explicitly states the shares were sold to pay taxes on vested restricted stock units, which is a common and preapproved outcome of equity compensation. The filing is singular, timely, and signed by the reporting officer. No additional derivative transactions or indirect ownership changes are reported, and the Form 4 does not indicate any unusual or material governance events.

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
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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^*

MOOK JOSHUA T.

(Last) (First) (Middle)

C/O HYLIION HOLDING CORP.

1202 BMC DRIVE, SUITE 100

(Street)

CEDAR PARK TX 78613

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Hyliion Holdings Corp. [ HYLN ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/25/2025

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

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 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
Common Stock	08/25/2025		F(1)		8,430	D	$1.77	521,049	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. Shares sold for the payment of a tax liability related to the vesting and distribution of restricted stock units.

Remarks:

	/s/ Joshua T. Mook	08/25/2025
	** 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).
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