C3is Inc. (CISS) files Form 6-K with preliminary Q2 2025 results

Rhea-AI Filing Summary

C3is Inc. filed a Form 6-K to furnish a press release with its preliminary financial and operating results for the three and six months ended June 30, 2025. The attached press release, dated September 2, 2025 and filed as Exhibit 99.1, contains these preliminary figures for both 2025 and 2024. The company notes that its independent accountants have not compiled, examined, or performed any procedures on these preliminary results, have not expressed any opinion or assurance, and disclaim any association with them. Most of this Form 6-K, including Exhibit 99.1 but excluding the section titled “CEO Dr. Diamantis Andriotis Commented:”, is incorporated by reference into C3is Inc.’s existing Form S-8 and Form F-3 registration statements.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of September 2025

Commission File Number 001-41717

C3IS INC.

(Translation of registrant’s name into English)

331 Kifissias Avenue Erithrea 14561 Athens, Greece

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ☒   Form 40-F ☐

INFORMATION CONTAINED IN THIS FORM 6-K REPORT

Financial and Operating Results for the three and six months ended June 30, 2025

Attached to this report on Form 6-K as Exhibit 99.1 is a copy of C3is Inc.’s (the “Company”) press release, dated September 2, 2025, announcing its preliminary financial and operating results for the three and six months ended June 30, 2025.

EXHIBIT INDEX

99.1 Press Release dated September 2, 2025

*****

Neither C3is Inc.’s independent accountants, nor any other independent accountants, have compiled, examined, or performed any procedures with respect to the preliminary financial results for the three and six months ended June 30, 2025 and 2024, nor have they expressed any opinion or any other form of assurance on such information, and assume no responsibility for, and disclaim any association with, the preliminary financial results.

This report on Form 6-K, including exhibit 99.1 hereto other than the section entitled “CEO Dr. Diamantis Andriotis Commented:”, is hereby incorporated by reference into the Company’s Registration Statement on Form S-8 (Reg. No. 333-273306) filed with the Securities and Exchange Commission on July 18, 2023 and Registration Statement on Form F-3 (Reg. No. 333- 285135) filed with the Securities and Exchange Commission on February 21, 2025.

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.

Date: September 2, 2025

C3IS INC.
By:		/s/ Nina Pyndiah
Name:		Nina Pyndiah
Title:		Chief Financial Officer

FAQ

What does C3is Inc. (CISS) report in this Form 6-K?

C3is Inc. furnishes a press release as Exhibit 99.1 that announces its preliminary financial and operating results for the three and six months ended June 30, 2025, and provides preliminary figures for the same periods in 2024.

Are the preliminary results in C3is Inc. (CISS) Form 6-K audited?

No. The company states that its independent accountants have not compiled, examined, or performed any procedures on the preliminary financial results and have not expressed any opinion or other assurance on this information.

What period do the C3is Inc. (CISS) preliminary results cover?

The preliminary results relate to C3is Inc.’s three and six months ended June 30, 2025, and also present preliminary information for the corresponding periods in 2024.

How is this C3is Inc. (CISS) Form 6-K used in existing registration statements?

The Form 6-K, including Exhibit 99.1 but excluding the section titled “CEO Dr. Diamantis Andriotis Commented:”, is incorporated by reference into C3is Inc.’s Form S-8 (Reg. No. 333-273306) and Form F-3 (Reg. No. 333-285135) registration statements.

What is Exhibit 99.1 in the C3is Inc. (CISS) Form 6-K filing?

Exhibit 99.1 is the press release dated September 2, 2025, in which C3is Inc. announces its preliminary financial and operating results for the specified 2025 and 2024 periods.

Who signed the C3is Inc. (CISS) Form 6-K?

The Form 6-K was signed on behalf of C3is Inc. by Nina Pyndiah, who is identified as the company’s Chief Financial Officer.