Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 6

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 6
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7376 |     | US$  | 0.7510 |     | US$  |       0.7617 |     | US$  | 0.8031 |
| Low for period                 |     | US$  |            0.6848 |     | US$  | 0.6937 |     | US$  |       0.7207 |     | US$  | 0.7217 |
| Rate at end of period          |     | US$  |            0.7183 |     | US$  | 0.6950 |     | US$  |       0.7561 |     | US$  | 0.7383 |
| Average rate for the period(1) |     | US$  |            0.7149 |     | US$  | 0.7300 |     | US$  |       0.7409 |     | US$  | 0.7686 |

| (1) | The average of the Bank of Canada rate on the last day of each month during the applicable period. |

S-1

SPECIAL NOTE REGARDING FORWARD-LOOKINGSTATEMENTS

This Prospectus Supplement, the Prospectus and the documents
incorporated by reference in the Prospectus contain “forward-looking information” and “forward-looking statements” (collectively, “forward-looking statements”) within the meaning of applicable securities
laws, including the “safe harbor” provisions of the Securities Act(Alberta), the United States Private Securities Litigation Reform Act of 1995,Section 21E of the United States Securities Exchange Act of 1934,as amended (the “U.S. Exchange Act”), and Section 27A of the United States Securities Act of 1933,as amended (the “Securities Act”). All forward-looking
statements are based on TransAlta’s beliefs as well as assumptions based on information available at the time the assumption was made and on management’s experience and perception of historical trends, current conditions and expected
further developments as well as other factors deemed appropriate in the circumstances. Forward-looking statements are not facts, but only predictions and generally can be identified by the use of statements
that include phrases such as “may”, “will”, “believe”, “expect”, “anticipate”, “intend”, “plan”, “foresee”, “potential”,
“enable”, “continue”, “