SCHEDULE: Summit Partners Boosts Klaviyo Stake to 20.87%

Summit Partners and its affiliated funds have increased their beneficial ownership in Klaviyo, Inc. to 20.87% of Series A Common Stock.

Summary

• Summit Partners, through various affiliated funds including 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., Summit Investors GE IX/VC IV, LLC, and Summit Investors GE IX/VC IV (UK), L.P., collectively hold beneficial ownership in Klaviyo, Inc.
• The aggregate amount beneficially owned by the Reporting Persons is 30,827,778 shares of Series A Common Stock.
• This ownership represents 20.87% of the outstanding Series A Common Stock.
• The calculation is based on 116,897,730 Series A Shares outstanding as of July 31, 2025, as reported in Klaviyo's Form 10-Q filed on August 5, 2025, plus the 30,827,778 Series A Shares issuable from Series B Shares held by Summit Holders.
• All beneficially owned shares are held with shared voting and shared dispositive power.
• The shares are issuable in respect of Series B Common Stock held by the Summit Holders.

Sentiment

Score: 5

Explanation: The filing is a routine disclosure of beneficial ownership, indicating a neutral sentiment. It confirms a significant, ongoing stake by a major investor.

Positives

• Increased significant institutional ownership by Summit Partners, indicating continued confidence in Klaviyo, Inc.

Negatives

• NA

Risks

• NA

Future Outlook

This filing is a disclosure of beneficial ownership and does not contain forward-looking statements or guidance from Klaviyo, Inc. or the reporting persons regarding the issuer's future performance.

Management Comments

• The investment committee of Summit Partners, L.P., currently composed of Peter Chung, Scott Collins, and Peter Rottier, may be deemed to have voting and dispositive authority over the reported securities.
• Each of the reporting entities and individuals disclaims beneficial ownership of the reported securities, except to the extent such securities are directly held by such entity.

Industry Context

This filing reflects a significant institutional investor's continued or increased stake in a publicly traded technology company, common in the investment landscape where private equity or growth equity firms maintain positions post-IPO.

Comparison to Industry Standards

• NA

Stakeholder Impact

• Shareholders: Provides transparency regarding a significant institutional holder's stake, potentially signaling long-term confidence.
• Management: Awareness of a large, influential shareholder's position.

Next Steps

• NA

Key Dates

Keywords

Klaviyo, Summit Partners, Beneficial Ownership, Schedule 13G, Series A Common Stock, Institutional Investor, Equity Stake, SEC Filing