[Form 4] Klaviyo, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Summit Partners entities reported transactions in Klaviyo, Inc. (KVYO). On 09/08/2025 the reporting parties converted 4,000,000 shares of Series B common stock into 4,000,000 shares of Series A common stock and simultaneously sold 4,000,000 shares of Series A common stock at $31.87 per share. Following the reported transactions the reporting group beneficially owns a total of 18,852,778 shares of Series A common stock on an indirect basis through multiple Summit funds and related entities. The filing discloses the ownership structure and the investment committee members who may have voting and dispositive authority.

Positive

• None.

Negative

• Disposition of 4,000,000 Series A shares sold at $31.87 per share on 09/08/2025, representing a material block sale by the reporting group
• Reduction in direct economic interest due to the reported sale, although indirect ownership remains significant

Insights

Financial Analyst

TL;DR: A large investor converted preferred shares and sold 4,000,000 Series A shares at $31.87, reducing their effective liquid stake while retaining significant indirect ownership.

The conversion of Series B to Series A and concurrent sale indicates liquidity realization by Summit-backed vehicles. The filed total of 18,852,778 Series A shares reflects continued substantial indirect ownership across multiple Summit funds. The transaction price of $31.87 for 4,000,000 shares quantifies the realized proceeds from the disposition. No forward-looking commentary or additional issuer disclosures are included in the Form 4.

Corporate Governance Expert

TL;DR: Multiple Summit entities disclosed a coordinated conversion and sale; governance notes clarify delegation and disclaimers of beneficial ownership.

The filing carefully explains the chain of control among Summit entities and notes delegation of voting and investment authority. It identifies the investment committee members who may be deemed to have voting/dispositive authority but includes standard disclaimers regarding beneficial ownership. The Form 4 documents a material block transaction by a major shareholder group without additional governance actions disclosed.

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
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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).

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)
09/08/2025

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	09/08/2025		C		4,000,000	A	(1)	4,000,000	I	See footnotes(2)(3)(4)
Series A Common Stock, par value $0.001 per share	09/08/2025		S		4,000,000	D	$31.87	0	I	See footnotes(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)	09/08/2025		C		4,000,000		(1)	(1)	Series A Common Stock, par value $0.001 per share	4,000,000	$0	18,852,778(5)	I	See footnotes(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) 11,142,414 shares of Series B Common Stock held by Fund IX-A, (ii) 6,957,168 shares of Series B Common Stock held by Fund IX-B, (iii) 687,035 shares of Series B Common Stock held by Kiwi Co-Invest Fund, (iv) 58,561 shares of Series B Common Stock held by Fund IX/VC IV, and (v) 7,600 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.	09/10/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Investors GE IX/VC IV, LLC	09/10/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Co-Invest (Kiwi), L.P.	09/10/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Growth Equity Fund IX-A, L.P.	09/10/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Investors GE IX/VC IV (UK), L.P.	09/10/2025
	/s/ Adam Hennessey, as attorney-in-fact for Summit Partners Growth Equity Fund IX-B, L.P.	09/10/2025
	** 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 did Summit Partners report on Form 4 for Klaviyo (KVYO)?

The filing reports that Summit entities converted 4,000,000 shares of Series B into 4,000,000 Series A shares and sold 4,000,000 Series A shares at $31.87 per share on 09/08/2025.

How many Klaviyo shares does the reporting group beneficially own after the transaction?

The Form 4 reports the reporting group beneficially owns 18,852,778 shares of Series A common stock on an indirect basis.

Which Summit entities are listed as reporting persons on the Form 4?

Reported entities include 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), L.P., and related Summit investor entities located at 222 Berkeley Street, Boston, MA.

Was the sale a secondary market disposition or a conversion-triggered sale?

The Form 4 shows a conversion of Series B to Series A (transaction code C) and a contemporaneous sale of 4,000,000 Series A shares (transaction code S) at $31.87; the document does not provide additional context beyond those entries.

Who within Summit is noted as having potential voting or dispositive authority?

The filing names investment committee members Peter Y. Chung, Scott C. Collins, and Peter L. Rottier as individuals who may be deemed to have voting and dispositive authority, with standard disclaimers.