[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Andrew P. Bialecki, Chief Executive Officer and director of Klaviyo, Inc. (KVYO), reported multiple transactions on August 26 and August 28, 2025. On August 26 he converted 226,702 shares of Series B into Series A and sold 216,433 shares at a weighted average price of $31.51 and 10,269 shares at a weighted average price of $31.21. On August 28 he converted 3,500,000 Series B shares into Series A and directed a bona fide gift of those 3,500,000 shares to a donor-advised fund; those gifted shares are subject to a 60-day lock-up following August 13, 2025. The August 26 trades were effected under a Rule 10b5-1 trading plan adopted May 20, 2025. The filing discloses various indirect holdings held in trusts and by his spouse, and includes certifications and signatures by an attorney-in-fact.

Positive

• Transactions effected under a Rule 10b5-1 plan, indicating pre-scheduled sales adopted May 20, 2025
• Full disclosure of conversion mechanics from Series B to Series A upon transfer is provided
• Gift to donor-advised fund documented with details on conversion and lock-up

Negative

• Insider sold 226,702 shares on August 26, 2025, at weighted-average prices around $31.21–$31.51
• Directed gift of 3,500,000 shares reduced the reporting person’s direct economic ownership (converted to Series A upon transfer)

Insights

Securities Analyst

TL;DR: CEO executed planned sales and a large gift that converted preferred shares into common stock and remains subject to a short lock-up.

The filing shows both Rule 10b5-1 plan-driven sales and a substantial directed gift of 3,500,000 shares to a donor-advised fund that automatically converted Series B into Series A upon transfer. The sales on August 26 totaled 226,702 shares at weighted-average prices in the low $31 range, executed under a pre-established trading plan, which indicates pre-planned liquidity rather than opportunistic insider selling. The separate August 28 transactions reflect a conversion plus an immediate charitable disposition that reduced economic ownership while triggering conversion mechanics in the company charter. Disclosed indirect holdings remain via multiple trusts and spouse ownership, with customary disclaimers regarding Section 16 beneficial ownership.

Corporate Governance Expert

TL;DR: Transactions are transparent and documented; gift and lock-up details are notable for governance review.

The report provides required disclosure of director/CEO activity including use of a 10b5-1 plan and the mechanics of converting Series B to Series A upon transfer. The 3,500,000-share gift to a donor-advised fund and the stated 60-day lock-up period are governance-relevant items: they affect immediate beneficial ownership and potential short-term float but are documented with conversion and lock-up language. Trust holdings and claimed disclaimers are properly noted. All material mechanics and prices reported are explicit in the filing.

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).

X

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^*

Bialecki Andrew

(Last) (First) (Middle)

C/O KLAVIYO, INC.

125 SUMMER STREET, 6TH FLOOR

(Street)

BOSTON MA 02110

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Klaviyo, Inc. [ KVYO ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/26/2025

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
Series A Common Stock	08/26/2025		C(1)		226,702	A	(2)	226,702	D
Series A Common Stock	08/26/2025		S(1)		216,433	D	$31.51(3)	10,269	D
Series A Common Stock	08/26/2025		S(1)		10,269	D	$31.21(4)	0	D
Series A Common Stock	08/28/2025		C		3,500,000	A	(5)	3,500,000	D
Series A Common Stock	08/28/2025		G(6)		3,500,000	D	$0	0	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
Series B Common Stock	(2)	08/26/2025		C(1)			226,702	(2)	(2)	Series A Common Stock	226,702	$0	74,546,574	D
Series B Common Stock	(2)	08/28/2025		C			3,500,000	(2)	(2)	Series A Common Stock	3,500,000	$0	71,046,574	D
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	11,945,830		11,945,830	I	By The Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023(7)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	517,006		517,006	I	By The Elizabeth L. Bialecki Irrevocable GST Trust of 2023(8)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	517,006		517,006	I	By The Andrew P. Bialecki Irrevocable GST Trust of 2023(9)
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	43,218		43,218	I	By spouse

Explanation of Responses:

1. These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on May 20, 2025.

2. Each share of the Issuer's Series B Common Stock, par value $0.001 per share ("Series B Common Stock"), is convertible at any time at the option of the holder into one share of the Issuer's Series A Common Stock, par value $0.001 per share ("Series A Common Stock"), and will automatically convert into one share of Series A Common Stock upon the occurrence of certain events as set forth in the Issuer's certificate of incorporation. The Series B Common Stock has no expiration date.

3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.225 to $32.22 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

4. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.17 to $31.22 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

5. The Reporting Person directed the transfer of 3,500,000 shares of their Series B Common Stock in connection with a bona fide gift to a donor-advised fund, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation.

6. Represents a bona fide gift of 3,500,000 shares of stock from the Reporting Person to a donor-advised fund. The Reporting Person directed the transfer of 3,500,000 shares of their Series B Common Stock, resulting in the automatic conversion of the shares into Series A Common Stock upon execution of the transfer pursuant to the Issuer's certificate of incorporation. These shares remain subject to a lock-up agreement for a period of 60 days following August 13, 2025, as required pursuant to a lock-up agreement the Reporting Person entered into with the underwriter in connection with a registered stock offering.

7. Shares held by the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, of which the Reporting Person serves as trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.

8. Shares held by the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person serves as a trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.

9. Shares held by the Andrew P. Bialecki Irrevocable GST Trust of 2023, of which the Reporting Person's spouse serves as a trustee. The Reporting Person disclaims Section 16 beneficial ownership of such shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed to be an admission that he has beneficial ownership of such shares for Section 16 or any other purpose.

Remarks:

	/s/ Landon Edmond, Attorney-in-Fact	08/28/2025
	** 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).
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.

FAQ

What transactions did Klaviyo (KVYO) CEO Andrew Bialecki report on Form 4?

He converted and acquired Series B shares that converted to Series A, sold 226,702 shares on 08/26/2025 at weighted-average prices ≈ $31.21–$31.51, and on 08/28/2025 converted and gifted 3,500,000 shares to a donor-advised fund.

Were any sales executed under a trading plan for KVYO insider filings?

Yes. The August 26 sales were effected pursuant to a Rule 10b5-1 trading plan adopted May 20, 2025.

What happened to the 3,500,000 shares gifted by the reporting person?

The 3,500,000 shares were transferred to a donor-advised fund, automatically converting Series B into Series A upon transfer, and remain subject to a 60-day lock-up following August 13, 2025.

Does the filing show indirect holdings for Andrew Bialecki?

Yes. The filing lists indirect holdings by multiple trusts and by his spouse, with disclaimers regarding Section 16 beneficial ownership.

What prices were reported for the August 26 sales?

Weighted-average prices were reported: sales ranged from $31.225 to $32.22 per share for one block (weighted average reported $31.51) and $31.17 to $31.22 per share for another block (weighted average reported $31.21).