SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

Klaviyo, Inc.

(Name of Issuer)

Series A Common Stock

(Title of Class of Securities)

49845K101

(CUSIP Number)

Shopify Strategic Holdings 3
112 North Curry St.,
Carson City, NV, 89703
6132416868

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

08/05/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. Checkbox not checked

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP Number(s):

49845K101

Name of reporting person

Shopify Strategic Holdings 3 LLC

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

OO, WC

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

NEVADA

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 33,405,047.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 33,405,047.00

Aggregate amount beneficially owned by each reporting person

33,405,047.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

20.83 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

CUSIP Number(s):

49845K101

Name of reporting person

Shopify Inc.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

CANADA (FEDERAL LEVEL)

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 33,405,047.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 33,405,047.00

Aggregate amount beneficially owned by each reporting person

33,405,047.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

20.83 %

Type of Reporting Person (See Instructions)

SCHEDULE 13D

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.

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.

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.

(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.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Shopify Strategic Holdings 3 LLC

Signature:	/s/ Jason Kilpela
Name/Title:	Jason Kilpela, Director
Date:	08/31/2026

Shopify Inc.

Signature:	/s/ Michael L. Johnson
Name/Title:	Michael L. Johnson, Secretary
Date:	08/31/2026