Klaviyo (NYSE: KVYO) CEO discloses Rule 10b5-1 insider stock sale filing

Rhea-AI Filing Summary

Klaviyo, Inc. insider Andrew P. Bialecki, who is a director, chief executive officer and 10% owner, reported a planned conversion and sale of company stock. On 12/22/2025, he converted 100,000 shares of Series B Common Stock into 100,000 shares of Series A Common Stock and then sold those 100,000 Series A shares in two transactions. He sold 93,066 shares at a weighted average price of $33.05 and 6,934 shares at a weighted average price of $31.94, leaving no directly held Series A shares after these transactions. The filing notes these trades were executed under a Rule 10b5-1 trading plan adopted on May 20, 2025, and that his remaining economic interest includes a large balance of Series B shares, which are convertible into Series A, including amounts held through various family trusts.

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

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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).

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)
12/22/2025

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	12/22/2025		C(1)		100,000	A	(2)	100,000	D
Series A Common Stock	12/22/2025		S(1)		93,066	D	$33.05(3)	6,934	D
Series A Common Stock	12/22/2025		S(1)		6,934	D	$31.94(4)	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)	12/22/2025		C(1)			100,000	(2)	(2)	Series A Common Stock	100,000	$0	69,568,889	D
Series B Common Stock	(2)							(2)	(2)	Series A Common Stock	7,517,410		7,517,410	I	By The Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023(5)
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(6)
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(7)
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 $32.38 to $33.35 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 $31.57 to $32.30 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. 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.

6. 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.

7. 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	12/23/2025
	** 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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FAQ

What insider transaction did Klaviyo (KVYO) report in this Form 4?

The filing reports that Andrew P. Bialecki, a director, chief executive officer and 10% owner of Klaviyo, Inc., converted 100,000 shares of Series B Common Stock into 100,000 shares of Series A Common Stock on 12/22/2025 and sold all 100,000 Series A shares in open-market transactions.

How many Klaviyo (KVYO) shares were sold and at what prices?

Bialecki sold a total of 100,000 Series A Common Stock shares. He sold 93,066 shares at a weighted average price of $33.05 per share and 6,934 shares at a weighted average price of $31.94 per share. The filing explains that each weighted average reflects multiple trades within stated price ranges.

Was the Klaviyo (KVYO) insider sale made under a Rule 10b5-1 trading plan?

Yes. The filing states that these transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 20, 2025. Such plans allow insiders to pre-schedule trades according to predefined instructions.

What is the relationship between Klaviyos Series B and Series A Common Stock?

The filing explains that each share of Series B Common Stock is convertible at any time at the option of the holder into one share of Series A Common Stock, and will automatically convert into one share of Series A Common Stock upon certain events described in the companys certificate of incorporation. The Series B Common Stock has no expiration date.

How many Klaviyo (KVYO) shares does the reporting person still beneficially own after these transactions?

The filing shows 69,568,889 shares of Series B Common Stock directly beneficially owned, which are convertible into Series A Common Stock. It also lists additional indirect holdings of Series B shares through several 2023 trusts and by the reporting persons spouse, corresponding to 7,517,410, 517,006, 517,006 and 43,218 Series A shares, respectively, upon conversion.

How are some of the Klaviyo (KVYO) shares held indirectly by the insider?

Certain shares are held through the Andrew P. Bialecki Grantor Retained Annuity Trust I of 2023, the Elizabeth L. Bialecki Irrevocable GST Trust of 2023, the Andrew P. Bialecki Irrevocable GST Trust of 2023, and by the insiders spouse. The filing states that Bialecki disclaims Section 16 beneficial ownership of those shares except to the extent of his pecuniary interest.