TransAlta (TAC) 6-K notes notice to mothball Sheerness Unit 1

Rhea-AI Filing Summary

TransAlta Corporation filed a Form 6-K as a foreign private issuer for December 2025. The report indicates that the company furnished an exhibit titled “TransAlta Provides Notice to Mothball Sheerness Unit 1,” signaling a planned change in the status of that generating unit. The filing was signed by Joel Hunter, Executive Vice President Finance and Chief Financial Officer.

Form 6-K: How Foreign Companies Report to the SEC →

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 December 2025

Commission File Number: 001-15214

TransAlta Corporation
(Translation of registrant's name into English)

Suite 1400, 1100 – 1st Street S.E., Calgary, Alberta, T2G 1B1
(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 [ X ]

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.

		TransAlta Corporation
		(Registrant)
Date: December 18, 2025		/s/ Joel Hunter
		Joel Hunter
		Executive Vice President Finance and Chief Financial Officer

EXHIBIT INDEX

Exhibit Number		Description
99.1		TransAlta Provides Notice to Mothball Sheerness Unit 1

FAQ

What did TransAlta Corporation (TAC) file in December 2025?

TransAlta Corporation filed a Form 6-K report as a foreign private issuer for the month of December 2025. This report furnishes an exhibit related to the planned mothballing of Sheerness Unit 1 and is signed by the company’s Chief Financial Officer.

What key event is referenced in TransAlta (TAC)’s December 2025 Form 6-K?

The Form 6-K references an exhibit titled “TransAlta Provides Notice to Mothball Sheerness Unit 1.” This indicates the company has provided formal notice regarding the mothballing of that specific unit, signalling a planned change in its operational status.

Who signed TransAlta Corporation (TAC)’s December 2025 Form 6-K?

The Form 6-K was signed by Joel Hunter, TransAlta Corporation’s Executive Vice President Finance and Chief Financial Officer. His signature confirms the company’s authorization of the filing and its contents, including the exhibit concerning Sheerness Unit 1.

What exhibit is included with TransAlta (TAC)’s December 2025 Form 6-K?

The filing includes Exhibit 99.1, titled “TransAlta Provides Notice to Mothball Sheerness Unit 1.” This exhibit appears to contain the detailed information about TransAlta’s notice and plans affecting that generating unit.

Under which annual report form does TransAlta Corporation (TAC) report?

TransAlta Corporation indicates that it files annual reports under cover of Form 40-F rather than Form 20-F. This classification reflects its status and reporting framework as a foreign private issuer in the United States.