Can I carry a net capital loss back to previous years in Canada?

This answer covers Canadian federal tax law, which applies in every province.

Yes. A net capital loss can be carried back three years and carried forward indefinitely, but it can be applied only against taxable capital gains. To carry it back, you use Part 5 of Form T1A (Request for Loss Carryback) and you do not file an amended return for the earlier year.

Losses from earlier years are applied oldest first, and the amount you apply is limited to the taxable capital gains in the year you apply it to. A loss you do not use stays available to carry forward with no time limit. A net capital loss for 2025 can go back to 2022, 2023 or 2024. Carrying a loss back reduces your taxable income but does not change your net income.

Some situations work differently. Carrying a loss back may reduce a lifetime capital gains deduction claimed in that year or later years. An allowable business investment loss can be deducted against other income, not just capital gains. Any unused excess becomes a non-capital loss. Because the rules depend on your own history of gains and claims, it is worth confirming the details with a lawyer or accountant.