Stepien to sell 23,529 Amprius (NYSE: AMPX) shares for tax withholding

Rhea-AI Filing Summary

Amprius Technologies, Inc. (AMPX) received a notice under Rule 144 from Thomas M. Stepien for a proposed sale of its common stock. The notice lists a planned sale of 23,529 shares of common stock through Morgan Stanley Smith Barney LLC, with an aggregate market value of $243,312.64 as of the notice. The sale relates to the release of 46,875 restricted stock units on 08/20/2026, with the filer stating the shares are to be sold to cover withholding taxes upon vesting of these awards. The notice also reports prior sales in the past three months, including 4,375 shares on 05/27/2026, 2,000 shares on 06/04/2026, and 8,000 shares on 08/24/2026.

Key Figures

Shares proposed to be sold: 23,529 shares of common stock Aggregate market value of proposed sale: $243,312.64 Restricted stock units released: 46,875 restricted stock units +3 more

6 metrics

Shares proposed to be sold 23,529 shares of common stock Proposed sale under Rule 144 via Morgan Stanley Smith Barney LLC

Aggregate market value of proposed sale $243,312.64 Aggregate market value of 23,529 shares referenced in the notice

Restricted stock units released 46,875 restricted stock units Release on 08/20/2026 related to compensation

Shares sold 05/27/2026 4,375 shares for $75,221.56 Common stock sale by Thomas M. Stepien during past 3 months

Shares sold 06/04/2026 2,000 shares for $41,940 Common stock sale by Thomas M. Stepien during past 3 months

Shares sold 08/24/2026 8,000 shares for $80,240 Common stock sale by Thomas M. Stepien during past 3 months

Key Terms

Rule 144, restricted stock units, withholding taxes

3 terms

Rule 144 regulatory

"See the definition of "person" in paragraph (a) of Rule 144."

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

restricted stock units financial

"Release of restricted stock units | Issuer | | | 46875 | 08/20/2026"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

withholding taxes financial

"SHARES TO BE SOLD TO COVER WITHHOLDING TAXES UPON VESTING"

Withholding taxes are amounts a payer or government takes out of payments — such as wages, interest, or dividends — before the recipient gets the money, functioning like a cashier keeping part of a bill to pay taxes on your behalf. For investors this matters because it reduces the cash they actually receive, affects net returns and yield calculations, and may require additional paperwork or treaty claims to recover or offset the withheld amount against final tax bills.

FAQ

What does the Form 144 filing disclose for Amprius Technologies, Inc. (AMPX)?

It discloses that Thomas M. Stepien filed a Rule 144 notice to sell 23,529 shares of Amprius Technologies, Inc. common stock, with an aggregate market value of $243,312.64, in connection with the vesting of restricted stock unit awards.

How many AMPX shares are proposed to be sold under this Form 144?

The notice lists a proposed sale of 23,529 shares of Amprius Technologies, Inc. common stock through Morgan Stanley Smith Barney LLC, with an indicated aggregate market value of $243,312.64 at the time referenced.

What is the relationship between the AMPX share sale and restricted stock units?

The filing states that the sale relates to the release of 46,875 restricted stock units on 08/20/2026 and that the shares are to be sold to cover withholding taxes upon vesting of those restricted stock unit awards.

What AMPX insider is involved in this Form 144 notice?

The Form 144 notice is for sales on behalf of Thomas M. Stepien, in connection with Amprius Technologies, Inc. (AMPX) common stock and the vesting of his restricted stock unit awards.

What AMPX share sales were reported for the past three months in the Form 144?

The notice reports prior sales of Amprius common stock by Thomas M. Stepien of 4,375 shares on 05/27/2026 for $75,221.56, 2,000 shares on 06/04/2026 for $41,940, and 8,000 shares on 08/24/2026 for $80,240.

Which broker is named for the proposed AMPX share sale in the Form 144?

The proposed sale of 23,529 shares of Amprius Technologies, Inc. common stock is listed as being through Morgan Stanley Smith Barney LLC, located at 1 New York Plaza, New York, NY.

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

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Available on EDGAR 08/25/2026 - 05:21 PM Accepted by SEC EDGAR 08/25/2026 - 05:21 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0002067233
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	AMPRIUS TECHNOLOGIES, INC.
SEC File Number	001-41314
Address of Issuer	1180 PAGE AVENUE FREMONT CALIFORNIA 94538
Phone	800-425-8803
Name of Person for Whose Account the Securities are To Be Sold	THOMAS M STEPIEN
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	OFFICER
Relationship to Issuer	DIRECTOR

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Morgan Stanley Smith Barney LLC 1 New York Plaza, 38th fl. New York NY 10004	23529	243312.64	146080618	08/21/2026	NYSE

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	08/20/2026	Release of restricted stock units	Issuer			46875	08/20/2026	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Thomas M. Stepien 1180 Page Ave. Fremont CA 94538	Common Stock	05/27/2026	4375	75221.56
Thomas M. Stepien 1180 Page Ave. Fremont CA 94538	Common Stock	06/04/2026	2000	41940
Thomas M. Stepien 1180 Page Ave. Fremont CA 94538	Common Stock	08/24/2026	8000	80240

144: Remarks and Signature

Remarks	SHARES TO BE SOLD TO COVER WITHHOLDING TAXES UPON VESTING OF RESTRICTED STOCK UNIT AWARDS
Date of Notice	08/25/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Thomas M. Stepien
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)