| Item 1. | Security and Issuer |
| (a) | Title of Class of Securities:
Series A Common Stock |
| (b) | Name of Issuer:
Klaviyo, Inc. |
| (c) | Address of Issuer's Principal Executive Offices:
125 Summer Street, 6th Floor, Boston,
MASSACHUSETTS
, 02110. |
Item 1 Comment:
Explanatory Note
This Amendment No. 4 (the "Amendment No. 4") to the Schedule 13D filed on December 11, 2023, as amended by Amendment No. 1 filed on July 30, 2024, Amendment No. 2 filed on February 21, 2025, and Amendment No. 3 filed on November 14, 2025 (as amended, the "Schedule 13D"), is being filed to report changes in the beneficial ownership reported by the Reporting Persons due to (i) the vesting of 344,383, 344,381, 344,383 and 344,382 Warrants on January 28, April 28, July 28 and October 28, 2026, respectively, and (ii) changes in the total number of Series A Common Stock outstanding since the filing of Amendment No. 3 to the Schedule 13D.
All items not described herein remain as previously reported in the Schedule 13D, and all capitalized terms used herein and not otherwise defined herein shall have the meanings ascribed to them in the Schedule 13D.
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| Item 2. | Identity and Background |
|
| (a) | Item 2 of the Schedule 13D is hereby amended by incorporating herein by reference the information set forth on the updated Annex A attached hereto. |
| Item 3. | Source and Amount of Funds or Other Consideration |
| | Item 3 of the Schedule 13D is hereby amended by adding the text below to the end of Item 3 of the Schedule 13D:
On January 28, April 28, and July 28 2026, 344,383, 344,381 and 344,383 of the Warrants held by SSH 3, respectively, vested and became exercisable for an equal number of shares of Series B Common Stock. SSH 3 exercised these Warrants on January 29, April 28 and August 31, 2026, respectively.
Additionally, 344,382 of the Warrants held by SSH 3 will vest and become exercisable for 344,382 shares of Series B Common Stock on October 28, 2026.
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| Item 5. | Interest in Securities of the Issuer |
| (a) | Item 5 is hereby amended and restated in its entirety as follows:
As of the date hereof, SSH 3 and Shopify Inc. beneficially own 33,405,047 shares of Series A Common Stock, representing approximately beneficial ownership of 20.83% of the outstanding Series A Common Stock, consisting of: (i) 17,317,491 shares of Series B Common Stock held directly by SSH 3, (ii) 344,382 Warrants held by SSH 3 that will vest and become exercisable for 344,382 shares of Series B Common Stock on October 28, 2026 and (iii) the Investment Option held by SSH 3, which is exercisable for an additional 15,743,174 Series B Common Stock. Each share of Series B Common Stock is convertible into one share of Series A Common Stock at any time at the option of the holder thereof.
Calculations of the percentage of the shares of Series A Common Stock beneficially owned by the Reporting Persons is based on (i) 126,937,933 shares of Series A Common Stock outstanding as of July 31, 2026, based on information set forth in the Form 10-Q filed by the Issuer with the Securities and Exchange Commission on August 5, 2026, (ii) 17,317,491 shares of Series A Common Stock issuable upon the conversion of Series B Common Stock held directly by SSH 3, where each share of Series B Common Stock is convertible into one share of Series A Common Stock, and (iii) 344,382 shares of Series A Common Stock issuable upon the conversion of Series B Common Stock underlying Warrants held by SSH 3 that will vest and become exercisable for 344,382 shares of Series B Common Stock on October 28, 2026 and (iv) the Investment Option held by SSH 3 to purchase 15,743,174 shares of Series B Common Stock, where each share of Series B Common Stock is convertible into one share of Series A Common Stock.
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| (b) | The number of shares as to which each Reporting Person has sole power to vote or to direct the vote, shared power to vote or to direct the vote, sole power to dispose or to direct the disposition, or shared power to dispose or to direct the disposition is set forth on rows 7 through 11 of the cover pages of this Amendment No. 4 and is incorporated herein by reference. |
| (c) | Except as set forth in this Schedule 13D, no transaction in Series A Common Stock has been effected by any of the Reporting Persons within the past 60 days. |
| (d) | To the best knowledge of the Reporting Persons, no one other than the Reporting Persons, or the partners, members, affiliates or shareholders of the Reporting Persons, has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Series A Common Stock reported herein as beneficially owned by the Reporting Persons. |
| (e) | Not applicable. |
| Item 7. | Material to be Filed as Exhibits. |
| | Annex A - Executive Officers and Directors of Shopify Inc. |
