C3is completes 1-for-5 reverse stock split

Split-adjusted CISS shares began trading November 9, and outstanding warrants and Series A preferred stock receive corresponding adjustments.

Available on EDGAR 11/09/2026 - 08:30 AM EST Accepted by SEC EDGAR 11/09/2026 - 08:30 AM EST Learn about SEC filing dates

Rhea-AI Filing Summary

C3is Inc. (CISS) effected a one-for-5 reverse stock split effective November 8, 2026. Outstanding common shares decreased from approximately 4.2 million to approximately 0.84 million. The shares began trading on a split-adjusted basis on The Nasdaq Capital Market on November 9.

No fractional shares were issued; stockholders entitled to fractions received cash in lieu. Outstanding warrants and Series A Convertible Preferred Stock will have their exercise or conversion prices and issuable share counts adjusted for the split. Certain warrant and preferred-stock prices are also subject to a further adjustment based on volume weighted average prices around the effective time.

Filing Explained

The further reset for the B-1, B-2, C-1 and C-2 warrants—and the Series A conversion price—uses the lowest daily VWAP during the five trading days immediately before and after the split, only if below the current exercise price, and B-1 and C-1 also allow a zero-cash exchange, while warrant share counts adjust to preserve the original aggregate exercise price.

Key Figures

Reverse stock split ratio: one-for-5 Outstanding common shares before split: approximately 4.2 million shares Outstanding common shares after split: approximately 0.84 million shares +1 more

4 metrics

Reverse stock split ratio one-for-5 Effective November 8, 2026

Outstanding common shares before split approximately 4.2 million shares Before the reverse stock split

Outstanding common shares after split approximately 0.84 million shares After the reverse stock split

Trading adjustment period five consecutive trading days Before and after the effective time for the further price adjustment

Key Terms

reverse stock split, volume weighted average price, zero cash exercise exchange option

3 terms

reverse stock split financial

"effected a one-for-5 reverse stock split"

A reverse stock split reduces a company's number of outstanding shares while raising the price per share proportionally, so the total value of each investor's holding is unchanged; a 1-for-10 split turns 100 shares worth $1 each into 10 shares worth $10 each. Companies often do this to regain compliance with an exchange's minimum price rule or to attract investors who avoid very low-priced stocks.

volume weighted average price financial

"lowest daily volume weighted average price"

The volume weighted average price (VWAP) is a way to measure the average price of a security, such as a stock, over a specific period, taking into account how many units were traded at each price. It’s similar to calculating the average cost of items bought when some are more frequently purchased than others. Investors use VWAP to assess whether a security is being bought or sold at a fair price during trading.

zero cash exercise exchange option financial

"exercisable pursuant to an alternative zero cash exercise exchange option"

Stock Split

1-for-5 reverse split · Effective November 8, 2026

Split Ratio 1-for-5 reverse split

Effective Date November 8, 2026

Shares Before Split 4,200,000

Shares After Split 840,000

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What was the CISS reverse stock split ratio and when did it take effect?

CISS effected a one-for-5 reverse stock split effective November 8, 2026. The common stock began trading on a split-adjusted basis on The Nasdaq Capital Market on November 9, 2026.

How many CISS common shares were outstanding after the reverse split?

C3is Inc. reported approximately 0.84 million outstanding common shares after the split, compared with approximately 4.2 million before it.

How were CISS warrants and Series A preferred stock adjusted?

Outstanding warrants and Series A Convertible Preferred Stock will be proportionately adjusted to increase exercise prices and reduce the number of shares issuable upon exercise. Certain warrant exercise prices, and accordingly the preferred-stock conversion price, are also subject to adjustment based on the lowest daily volume weighted average price over five consecutive trading days before and after the split’s effective time, if lower than the then-current exercise price.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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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 November 2026

Commission File Number 001-41717

C3IS INC.

(Translation of registrant’s name into English)

331 Kifissias Avenue Kifissia 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

Reverse Stock Split

On November 6, 2026, C3is Inc. (the “Company”) filed an amendment to its Restated Articles of Incorporation, to effectuate a reverse stock split of the Company’s issued and outstanding shares of common stock, par value of $0.01 per share. A copy of the amendment is attached hereto as Exhibit 4.1.

Effective as of 11:59 p.m. Eastern time on November 8, 2026, the Company effected a one-for-5 reverse stock split of its shares of common stock, and the Company’s common stock began trading on a split-adjusted basis on The Nasdaq Capital Market as of the opening of trading on November 9, 2026. The reverse stock split reduced the number of outstanding shares of the Company’s common stock from approximately 4.2 million shares to approximately 0.84 million shares and affected all outstanding shares of common stock. No fractional shares were issued in connection with the reverse split. Stockholders who would otherwise hold a fractional share of the Company’s common stock received a cash payment in lieu of such fractional share. The Company’s outstanding warrants and Series A Convertible Preferred Stock will be proportionately adjusted to increase the exercise price and reduce the number of shares issuable upon exercise to reflect the reverse stock split.

The exercise price of the Class B-1, B-2, C-1 and C-2 Warrants, and accordingly the conversion price of the Series A Convertible Preferred Stock, will be further adjusted to the lowest daily volume weighted average price during the period commencing five consecutive trading days immediately preceding and the five consecutive trading days following the effective time of the reverse split (if lower than the then current exercise price), with the Class B-1 and C-1 warrants also being exercisable pursuant to an alternative zero cash exercise exchange option, and the number of shares of common stock issuable upon exercise will be proportionately adjusted such that the aggregate exercise price of such warrants as of their original issuance date will remain unchanged.

The par value and other terms of the Company’s shares of common stock were not affected by the reverse stock split. The Company’s post-reverse split common shares have a new CUSIP number, Y18284508, and continue to trade on the Nasdaq Capital Market under the symbol “CISS”.

A copy of the new form of stock certificate for the Company’s post-reverse stock split shares of common stock is attached hereto as Exhibit 4.2.

*****

This report on Form 6-K 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.

EXHIBIT INDEX

4.1		Articles of Amendment to Restated Articles of Incorporation.
4.2		Form of Common Stock Certificate.

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: November 9, 2026

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

Filing Exhibits & Attachments

2 documents

Other Documents

• EX-4.1 EX-4.1 7.9 KB
• EX-4.2 EX-4.2 15.5 KB