[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Andrew P. Bialecki, Klaviyo, Inc. CEO, director and reported 10% owner, effected transactions on 09/09/2025 under a Rule 10b5-1 plan adopted May 20, 2025. The reporting person caused the conversion/acquisition of 220,481 shares of Series B Common Stock and the subsequent sale of 220,481 shares of Series A Common Stock at a weighted average price of $31.96 per share. The filing discloses various indirect holdings through trusts and lists total Series A Common Stock reported following the transactions as 70,602,789 shares directly and additional indirect holdings through identified trusts.

Positive

• Transactions were executed under a Rule 10b5-1 plan, indicating a pre-established, documented trading arrangement
• Substantial reported aggregate holdings remain with 70,602,789 shares of Series A Common Stock listed as direct ownership following the transactions

Negative

• Sale of 220,481 shares on 09/09/2025 at a weighted average price of $31.96 reduced the specific converted lot to zero direct shares reported in Table I

Insights

Securities Analyst

TL;DR: Insider executed preplanned sale of 220,481 shares at ~$31.96 under a 10b5-1 plan; substantial aggregate holdings remain.

The Form 4 shows a conversion and immediate sale on 09/09/2025 pursuant to a Rule 10b5-1 trading plan adopted May 20, 2025. The reporting person sold 220,481 shares at a weighted average price of $31.96. The filing also lists substantial remaining direct Series A holdings of 70,602,789 shares and several indirect trust holdings. For investors, this is a routine disclosure of an executed 10b5-1 plan rather than an unscheduled open-market sale.

Corporate Governance Expert

TL;DR: Transaction appears compliant with governance norms: conversion, then sale under documented 10b5-1 plan.

The report identifies the transactions as effected pursuant to a documented Rule 10b5-1 plan, which provides an affirmative defense to insider trading allegations when conditions are met. The filing also includes customary disclaimers regarding beneficial ownership of trust-held shares and identifies the reporting person’s roles as CEO and director, and as a trustee for certain trusts holding shares.

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)
09/09/2025

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	09/09/2025		C(1)		220,481	A	(2)	220,481	D
Series A Common Stock	09/09/2025		S(1)		220,481	D	$31.96(3)	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)	09/09/2025		C(1)			220,481	(2)	(2)	Series A Common Stock	220,481	$0	70,602,789	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(4)
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(5)
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(6)
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 $31.44 to $32.345 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. 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.

5. 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.

6. 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	09/11/2025
	** 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 did Andrew Bialecki report on Form 4 for KVYO?

The Form 4 reports the conversion/acquisition of 220,481 Series B shares and the sale of 220,481 Series A shares on 09/09/2025 executed under a Rule 10b5-1 plan.

What price did the insider receive for the KVYO shares sold?

The shares were sold at a weighted average price of $31.96 per share, with individual trades in the range $31.44 to $32.345.

When was the 10b5-1 plan adopted for these KVYO transactions?

The Rule 10b5-1 trading plan was adopted by the reporting person on May 20, 2025, as stated in the filing.

How many KVYO shares does the filing show as directly owned after the transactions?

The filing lists 70,602,789 shares of Series A Common Stock as direct beneficial ownership following the reported transactions.

Are there indirect holdings disclosed in the Form 4 for KVYO?

Yes. The filing discloses indirect holdings through multiple trusts, including amounts of 11,945,830, 517,006, 517,006, and 43,218 Series A shares for named trusts and a spouse.