UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934

November 30, 2022

Date of report (date of earliest event reported)

Digi International Inc.

(Exact name of registrant as specified in its charter)

(952) 912-3444

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

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

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter):

Emerging growth company ¨

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. ¨

On November 30, 2022, the Audit Committee of the Board of Directors of Digi International Inc. dismissed Grant Thornton LLP, which had been serving as our independent registered public accounting firm. On the same date, the Audit Committee approved the engagement of Deloitte & Touche LLP to audit our financial statements for the fiscal year ending September 30, 2023, subject to Deloitte & Touche LLP’s standard client acceptance procedures and execution of an engagement letter. The decisions were recommended and approved by the Audit Committee after conducting a process that included consideration of auditor rotation.

During the fiscal years ended September 30, 2022 and September 30, 2021 and the subsequent interim period through and including November 30, 2022, there were no (i) disagreements between us and Grant Thornton LLP on any matter of accounting principles or practices, financial statement disclosure, or auditing scope or procedure, which disagreements, if not resolved to the satisfaction of Grant Thornton LLP, would have caused it to make reference thereto in its reports on the financial statements for such years or (ii) “reportable events” as that term is defined in Item 304(a)(1)(v) of Regulation S-K. The reports of Grant Thornton LLP on our consolidated financial statements and the effectiveness of internal control over financial reporting, which were included in our Annual Reports on Form 10-K for the fiscal years ended September 30, 2022 and 2021, did not contain an adverse opinion or disclaimer of opinion and were not qualified or modified as to uncertainty, audit scope or accounting principles.

We have provided Grant Thornton LLP with a copy of the foregoing disclosure and requested that they furnish a letter addressed to the Securities and Exchange Commission stating whether or not it agrees with the above statements. A copy of the letter from Grant Thornton LLP is attached as Exhibit 16.1 to this Current Report on Form 8-K.

During the fiscal years ended September 30, 2022 and September 30, 2021 and the subsequent interim period through and including November 30, 2022, we did not consult with Deloitte & Touche LLP regarding either (i) the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on our financial statements, and no written report or oral advice was provided that Deloitte & Touche LLP concluded was an important factor considered by us in reaching a decision as to the accounting, auditing or financial reporting issue; or (ii) any matter that was either the subject of a “disagreement” as that term is defined in Item 304(a)(1)(iv) of Regulation S-K or a “reportable event” as that term is defined in Item 304(a)(1)(v) of Regulation S-K.

SIGNATURES

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

Date: December 5, 2022