[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Klaviyo, Inc. (KVYO) Form 4 reports that Summit Partners-affiliated entities effected transactions on 08/25/2025. The filing shows 975,000 shares acquired as Series B common stock (convertible into Series A) and a contemporaneous sale of 975,000 shares of Series A common stock at $30.01 per share. The reporting group collectively beneficially owns 22,852,778 shares (on an indicated Series A-equivalent basis) across multiple Summit funds. The filing is executed by Adam Hennessey as attorney-in-fact for the Summit reporting persons and includes explanatory footnotes describing the ownership and control structure within the Summit Partners organization.

Insights

Financial Analyst

TL;DR: Summit affiliated funds recorded an intra-structure conversion/acquisition and an offsetting sale of 975,000 shares at $30.01, with total beneficial ownership of 22,852,778 shares.

The transaction date is 08/25/2025 and the Form 4 discloses both acquisition of convertible Series B shares and a sale of Series A shares for $30.01 each. The filing clarifies that Series B shares convert 1:1 into Series A and lists the detailed ownership chain among Summit entities and delegated voting/investment authority. Transactions are reported for multiple Summit funds and executed by an attorney-in-fact.

Corporate Governance Expert

TL;DR: The filing documents a reported conversion-related acquisition and an equal-sized sale, with full disclosure of voting and dispositive authority within the Summit structure.

The Form 4 includes comprehensive footnotes describing the managerial and investment-delegation relationships among Summit entities and names the investment committee members who may be deemed to have voting/dispositive authority. Signatures are provided by the attorney-in-fact, and the filing follows Section 16 reporting requirements without indicating any amendment or missing disclosures in the provided content.

Insider Trade Summary

Net Seller: 975,000 shares ($29,259,750)

Net Sell 3 txns

Insider SUMMIT PARTNERS L P, Summit Partners Growth Equity Fund IX-A, L.P., Summit Partners Growth Equity Fund IX-B, L.P., Summit Partners Co-Invest (Kiwi), LP, SUMMIT INVESTORS GE IX/VC IV, LLC, SUMMIT INVESTORS GE IX/VC IV (UK), L.P.

Role 10% Owner | 10% Owner | 10% Owner | 10% Owner | 10% Owner | 10% Owner

Sold 975,000 shs ($29.26M)

Type	Security	Shares	Price	Value
Conversion	Series B Common Stock, par value $0.001 per share	975,000	$0.00	--
Conversion	Series A Common Stock, par value $0.001 per share	975,000	$0.00	--
Sale	Series A Common Stock, par value $0.001 per share	975,000	$30.01	$29.26M

Holdings After Transaction: Series B Common Stock, par value $0.001 per share — 22,852,778 shares (Indirect, See footnote); Series A Common Stock, par value $0.001 per share — 975,000 shares (Indirect, See footnote)

Footnotes (1)

1. The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation. Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)"). (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P. The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement. Consists of (i) 13,506,504 shares of Series B Common Stock held by Fund IX-A, (ii) 8,433,272 shares of Series B Common Stock held by Fund IX-B, (iii) 832,803 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 70,986 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 9,213 shares of Series B Common Stock held by Fund IX/VC IV (UK).

Form 4 Insider Transactions: What Each Field Means →

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).

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^*

SUMMIT PARTNERS L P

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
08/25/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	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, par value $0.001 per share	08/25/2025		C		975,000	A	(1)	975,000	I	See footnote(2)(3)(4)
Series A Common Stock, par value $0.001 per share	08/25/2025		S		975,000	D	$30.01	0	I	See footnote(2)(3)(4)

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, par value $0.001 per share	(1)	08/25/2025		C		975,000		(1)	(1)	Series A Common Stock, par value $0.001 per share	975,000	$0	22,852,778(5)	I	See footnote(2)(3)(4)

1. Name and Address of Reporting Person^*

SUMMIT PARTNERS L P

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Summit Partners Growth Equity Fund IX-A, L.P.

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Summit Partners Growth Equity Fund IX-B, L.P.

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Summit Partners Co-Invest (Kiwi), LP

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

SUMMIT INVESTORS GE IX/VC IV, LLC

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

SUMMIT INVESTORS GE IX/VC IV (UK), L.P.

(Last) (First) (Middle)

222 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

Explanation of Responses:

1. The Series B common stock, par value $0.001 per share ("Series B Common Stock"), is convertible into an equal number of shares of Series A common stock, par value $0.001 per share ("Series A Common Stock"), at any time, at the holder's election, and has no expiration date. Each share of Series B Common Stock will automatically convert into Series A Common Stock upon the earlier of (i) the date specified by 66-2/3% of the outstanding shares of Series B Common Stock, voting as a single series; (ii) following the seventh anniversary of the closing of Klaviyo, Inc.'s (the "Company") initial public offering; or (iii) any transfer, whether or not for value, except for certain permitted transfers described in the Company's certificate of incorporation.

2. Summit Partners, L.P. is the manager of Summit Partners GE IX, LLC, which is the general partner of Summit Partners GE IX, LP, which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. ("Fund IX-A") and Summit Partners Growth Equity Fund IX-B, L.P. ("Fund IX-B"). Summit Partners, L.P. is the managing member of Summit Partners Co-Invest Kiwi GP, LLC, which is the general partner of Summit Partners Co-Invest (Kiwi), L.P. ("Kiwi Co-Invest Fund"). Summit Master Company, LLC is the general partner of Summit Partners, L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC ("Fund IX/VC IV") and the general partner of Summit Investors GE IX/VC IV (UK), L.P. ("Fund IX/VC IV (UK)").

3. (continued from footnote 2) Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC, has delegated voting and investment decisions with respect to the securities held by Fund IX/VC IV and Fund IX/VC IV (UK) to Summit Partners, L.P.

4. The investment committee of Summit Partners, L.P., is currently composed of Peter Y. Chung, Scott C. Collins, and Peter L. Rottier, who may be deemed to have voting and dispositive authority over, and therefore beneficial ownership of, the reported securities. Each of the foregoing entities, Mr. Chung, Mr. Collins, and Mr. Rottier disclaims beneficial ownership of the shares, except to the extent of such person's or entity's pecuniary interest therein and the filing of this statement shall not be deemed an admission that any of the foregoing entities or persons are, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this statement.

5. Consists of (i) 13,506,504 shares of Series B Common Stock held by Fund IX-A, (ii) 8,433,272 shares of Series B Common Stock held by Fund IX-B, (iii) 832,803 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 70,986 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 9,213 shares of Series B Common Stock held by Fund IX/VC IV (UK).

	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners, L.P.	08/27/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Investors GE IX/VC IV, LLC	08/27/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Co-Invest (Kiwi), L.P.	08/27/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Growth Equity Fund IX-A, L.P.	08/27/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Investors GE IX/VC IV (UK), L.P.	08/27/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Growth Equity Fund IX-B, L.P.	08/27/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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