Leigh A. Vosseller - 15 May 2026 Form 4 Insider Report for TANDEM DIABETES CARE INC (TNDM)

Reporting relationship: EVP & CHIEF FINANCIAL OFFICER
Issuer ticker: TNDM
Reported as of: 15 May 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 19 May 2026, 16:03:50 UTC
Prior SEC filing: 19 Feb 2026
Next SEC filing: 02 Jun 2026
Source filing: View source filing
Reporting owner signature: /s/ Shannon M. Hansen, Attorney-in-Fact for Leigh A. Vosseller

Key filing fact

Leigh A. Vosseller filed Form 4 for TANDEM DIABETES CARE INC (TNDM) on 19 May 2026.

Key facts

This page summarizes Leigh A. Vosseller's Form 4 filing for TANDEM DIABETES CARE INC (TNDM).
10 reported transactions and 3 derivative rows are listed below.
Accepted by SEC: 19 May 2026, 16:03.

Change

Previous filing in this sequence was filed on 19 Feb 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001726322 Primary reporting owner

Vosseller Leigh

Relationship: EVP & CHIEF FINANCIAL OFFICER
Address: 12400 HIGH BLUFF DRIVE, SAN DIEGO
Signature: /s/ Shannon M. Hansen, Attorney-in-Fact for Leigh A. Vosseller
Signature date: 19 May 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

TNDM transaction

Common Stock

Options Exercise

Transaction value
Shares: +1,503
Change %: +3.8%
Price: $0.000000^*
Shares after: 40,914
Date: 15 May 2026
Ownership: Direct

TNDM transaction

Common Stock

Tax liability

Transaction value
Shares: -540
Change %: -1.3%
Price: $12.82^*
Shares after: 40,374
Date: 15 May 2026
Ownership: Direct
Footnotes: F1

TNDM transaction

Common Stock

Options Exercise

Transaction value
Shares: +1,496
Change %: +3.7%
Price: $0.000000^*
Shares after: 41,870
Date: 15 May 2026
Ownership: Direct

TNDM transaction

Common Stock

Tax liability

Transaction value
Shares: -537
Change %: -1.3%
Price: $12.82^*
Shares after: 41,333
Date: 15 May 2026
Ownership: Direct
Footnotes: F1

TNDM transaction

Common Stock

Options Exercise

Transaction value
Shares: +10,496
Change %: +25%
Price: $0.000000^*
Shares after: 51,829
Date: 15 May 2026
Ownership: Direct

TNDM transaction

Common Stock

Tax liability

Transaction value
Shares: -3,766
Change %: -7.3%
Price: $12.82^*
Shares after: 48,063
Date: 15 May 2026
Ownership: Direct
Footnotes: F1

TNDM transaction

Common Stock

Award

Transaction value
Shares: +1,336
Change %: +2.8%
Price: $10.90^*
Shares after: 49,399
Date: 15 May 2026
Ownership: Direct
Footnotes: F2

TNDM holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 25,580
Date: 15 May 2026
Ownership: Leigh A. Vosseller Trust
Footnotes: F3

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

TNDM transaction Derivative

Restricted Stock Unit

Options Exercise

Transaction value
Shares: -1,503
Change %: -100%
Price: $0.000000^*
Shares after: 0
Date: 15 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 1,503
Exercise price
Footnotes: F4, F5, F6

TNDM transaction Derivative

Restricted Stock Unit

Options Exercise

Transaction value
Shares: -1,496
Change %: -20%
Price: $0.000000^*
Shares after: 5,982
Date: 15 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 1,496
Exercise price
Footnotes: F5, F7, F8

TNDM transaction Derivative

Restricted Stock Unit

Options Exercise

Transaction value
Shares: -10,496
Change %: -33%
Price: $0.000000^*
Shares after: 20,992
Date: 15 May 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 10,496
Exercise price
Footnotes: F5, F9, F10

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 10 footnotes

Footnote F1

Shares withheld by Tandem Diabetes Care Inc. (the Company) to satisfy tax withholding requirements on vesting of restricted stock units (RSU). No shares were sold.

Footnote F2

The reporting person is voluntarily reporting the acquisition of shares of common stock pursuant to the Tandem Diabetes Care, Inc. Amended and Restated 2013 Employee Stock Purchase Plan (ESPP), for the ESPP purchase period of November 18, 2025, through May 15, 2026. This transaction is also exempt under Rule 16b-3(c).

Footnote F3

The securities are held by the Leigh A. Vosseller Trust dated January 17, 2010, of which Leigh Vosseller is the Trustee.

Footnote F4

Awarded on May 25, 2023 pursuant to the Tandem Diabetes Care Inc. 2023 Long-Term Incentive Plan, as amended, and agreements related thereto (the 2023 Plan).

Footnote F5

Each RSU represents a contingent right to receive either one share of common stock of the Issuer or cash in lieu thereof, at the Issuer's discretion, in accordance with the terms of the 2023 Plan.

Footnote F6

RSU vest as to thirty-three percent (33%) of the total number of shares subject to the RSU on 5/15/2024, and the remaining shares shall vest in eight (8) equal quarterly installments thereafter.

Footnote F7

Awarded on May 23, 2024 pursuant to the 2023 Plan.

Footnote F8

RSU vest as to thirty-three percent (33%) of the total number of shares subject to the RSU on 5/15/2025, and the remaining shares shall vest in eight (8) equal quarterly installments thereafter.

Footnote F9

Awarded on May 30, 2025 pursuant to the 2023 Plan.

Footnote F10

RSU vest as to thirty-three percent (33%) of the total number of shares subject to the RSU on 5/15/2026, and the remaining shares shall vest in eight (8) equal quarterly installments thereafter.