UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q/A

(Amendment No. 1)

For the Quarterly Period Ended September 30, 2018

OR

For the Transition Period from              to                 

Commission File Number 001-36189

Tandem Diabetes Care, Inc.

(Exact name of registrant as specified in its charter)

(858) 366-6900

Registrant’s telephone number, including area code

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  ☒    No  ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).    Yes  ☒    No  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.                                                                                                                                                                            ☒    
            

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ☐    No   ☒

As of October 24, 2018, there were 57,369,283  shares of the registrant’s Common Stock outstanding.

EXPLANATORY NOTE

The sole purpose of this Amendment No. 1 (the “Amendment”) to the Tandem Diabetes Care, Inc. Quarterly Report on Form 10-Q (the “Original Form 10-Q”) for the period ended September 30, 2018, as filed with the Securities and Exchange Commission (the “SEC”) on November 1, 2018, is to revise the hierarchical headings and certain formatting within Exhibit 10.5, previously included with the Original Form 10-Q, to conform the as filed version of Exhibit 10.5 with the execution version.

This Amendment contains only the cover page, the Explanatory Note, Item 6. Exhibits, the Signature Page and the officer certifications required by Section 302 of the Sarbanes-Oxley Act of 2002. Except as described above, no other changes have been made to the Original Form 10-Q.

This Amendment does not reflect events that may have occurred subsequent to the original filing date and does not modify or update in any way disclosures made in the Original Form 10-Q. Accordingly, this Amendment should be read in conjunction with the Original Form 10-Q and our other filings with the SEC.

2

.

3

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

4