[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Andrew P. Bialecki, Klaviyo, Inc. director, CEO and reported 10% owner, effected transactions on 09/02/2025 under a Rule 10b5-1 trading plan adopted May 20, 2025. He converted 223,304 shares of Series B common stock into Series A common stock and subsequently sold the converted shares in two sets of transactions: 128,877 shares at a weighted average price of $31.18 (sales ranged $30.88–$31.87) and 94,427 shares at a weighted average price of $30.76 (sales ranged $30.61–$30.87), resulting in 0 direct Series A shares remaining from this block. The Form 4 discloses additional indirect holdings of Series A shares held in several family trusts and by a spouse where the reporting person disclaims beneficial ownership except to the extent of any pecuniary interest.

Positive

• Transactions executed under a Rule 10b5-1 plan, adopted May 20, 2025, which indicates pre-authorized trading
• Full disclosure of trustee and trust holdings with standard disclaimers regarding Section 16 beneficial ownership

Negative

• Material insider sales totaling 223,304 shares sold on 09/02/2025, which represent a significant disposition by a 10% owner and the CEO
• Weighted average sale prices ranged approximately $30.61 to $31.87, which may be perceived negatively by some investors despite 10b5-1 plan context

Insights

Securities Analyst

TL;DR: CEO sold 223,304 converted shares under a pre-established 10b5-1 plan, realizing proceeds near $31 per share; no direct shares remained from that block.

The transactions were executed pursuant to a Rule 10b5-1 plan adopted May 20, 2025, which indicates pre-authorized sales rather than ad hoc trading. The Form 4 shows a full conversion of 223,304 Series B shares and subsequent disposition in two tranches at weighted average prices of $31.18 and $30.76. For investors, these sales are material in size but accompanied by the 10b5-1 disclosure, which reduces the implication of opportunistic insider timing. The filing also lists substantial indirect holdings via multiple trusts and a spouse, which may be relevant when assessing total insider exposure.

Corporate Governance Expert

TL;DR: Large insider sales were reported but were conducted under a documented 10b5-1 plan and accompanied by standard trust disclaimers.

The report appropriately discloses the reporting person's roles (Director, CEO, 10% owner) and identifies the transactions as covered by a Rule 10b5-1 plan adopted on May 20, 2025. The explanatory footnotes clarify conversions of Series B to Series A and state trustee relationships for several trusts holding Series A shares, with standard disclaimers of Section 16 beneficial ownership except for any pecuniary interest. The mechanics and disclosures comply with Form 4 requirements; governance reviewers will note the combination of role and volume but also the 10b5-1 context.

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)
09/02/2025

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	09/02/2025		C(1)		223,304	A	(2)	223,304	D
Series A Common Stock	09/02/2025		S(1)		128,877	D	$31.18(3)	94,427	D
Series A Common Stock	09/02/2025		S(1)		94,427	D	$30.76(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)	09/02/2025		C(1)			223,304	(2)	(2)	Series A Common Stock	223,304	$0	70,823,270	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(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 $30.88 to $31.87 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 $30.61 to $30.87 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	09/04/2025
	** 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 Klaviyo (KVYO) insider Andrew Bialecki report on Form 4?

The Form 4 reports conversion of 223,304 Series B shares to Series A and sales of those shares on 09/02/2025 under a Rule 10b5-1 plan.

How many shares did Andrew Bialecki sell and at what prices?

He sold 128,877 shares at a weighted average of $31.18 (range $30.88–$31.87) and 94,427 shares at a weighted average of $30.76 (range $30.61–$30.87).

Was the selling done under a prearranged plan?

Yes. The Form 4 states the transactions were effected pursuant to a Rule 10b5-1 trading plan adopted on May 20, 2025.

Does Andrew Bialecki still have indirect holdings in Klaviyo?

Yes. The filing discloses indirect holdings of Series A shares held in several trusts and by a spouse, with specific amounts reported in the filing.

Does the Form 4 indicate any undisclosed or unusual items?

No. The filing includes explanatory footnotes about conversion mechanics, price ranges for sales, and standard disclaimers for trust-held shares.