Klaviyo owner plans $35.6M stock sale

The listed securities were acquired in pre-IPO transactions on September 20, 2023, through purchases of equity interests in Klaviyo.

Available on EDGAR 11/09/2026 - 09:56 PM EST Accepted by SEC EDGAR 11/09/2026 - 09:55 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

Klaviyo, Inc. (KVYO) owner Summit Partners Growth Equity Fund IX-B, L.P. reported 1,712,242 shares of Series A common stock to be sold, with an approximate sale date of November 9, 2026 and an aggregate market value of $35,648,878.44. The owner also reported selling 1,845,131 shares on August 11, 2026, for gross proceeds of $33,876,605.18.

Key Figures

Shares to be sold: 1,712,242 shares Aggregate Market Value: $35,648,878.44 Shares sold: 1,845,131 shares +1 more

4 metrics

Shares to be sold 1,712,242 shares Approximate sale date November 9, 2026

Aggregate Market Value $35,648,878.44 Shares to be sold

Shares sold 1,845,131 shares August 11, 2026

Gross Proceeds $33,876,605.18 Sale on August 11, 2026

Key Terms

Aggregate Market Value, par value, pre-IPO transactions

3 terms

Aggregate Market Value financial

"Aggregate Market Value"

Aggregate market value is the combined price you would pay to buy all outstanding shares of a company or all companies in a group at current market prices — essentially the sum of each stock’s market capitalization. It matters to investors because it shows the overall size and weight of an investment or sector (like the total cost to buy every piece of a puzzle), helps compare scale across companies or markets, and influences index composition and risk exposure.

par value financial

"par value $0.001 per share"

Par value is the fixed amount printed on a bond or stock that represents its original value when issued. It’s like the face value of a coin or bill—what the issuer promises to pay back or the starting price of a stock—though it often doesn’t change with market prices. It matters because it helps determine certain financial details, like how much the company will pay back at maturity.

pre-IPO transactions financial

"Pre-IPO transactions."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many KVYO shares does Summit Partners Growth Equity Fund IX-B plan to sell?

Summit Partners Growth Equity Fund IX-B, L.P., identified as an owner of Klaviyo, reported 1,712,242 shares of Series A common stock to be sold, with an approximate sale date of November 9, 2026 and an aggregate market value of $35,648,878.44.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001634426
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	Klaviyo, Inc.
SEC File Number	001-41806
Address of Issuer	125 Summer Street, 6th Floor Boston MASSACHUSETTS 02110
Phone	617-213-1788
Name of Person for Whose Account the Securities are To Be Sold	Summit Partners Growth Equity Fund IX-B, L.P.
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Owner

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Series A common stock, par value $0.001 per share	Barclays Capital Inc. 745 7th Avenue New York NY 10019	1712242	35648878.44	130150680	11/09/2026	NYSE

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Series A common stock, par value $0.001 per share	09/20/2023	Pre-IPO transactions.	Klaviyo, Inc.			20086500	09/20/2023	Equity interests in the Issuer were purchased pre-IPO.

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Summit Partners Growth Equity Fund IX-B, L.P. 222 Berkeley St 18th FL Boston MA 02116	Series A common stock, par value $0.001 per share	08/11/2026	1845131	33876605.18

144: Remarks and Signature

Remarks
Date of Notice	11/09/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Adam Hennessey
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)