Net capital losses of a current year can be carried back to any 3 previous years within the current year Turbotax return.

You'll navigate to the "Losses" section within your 2024 Turbotax product, indicate you want to "Request a loss carryback", and continue until you reach the "Net Capital Loss Carryback" screen, where you will see entry fields to apply the available net capital loss to any of the three previous years. 

You can enter the amount of the net capital loss  you want to apply to each year.   This process files a T1Adj for the year the loss is applied, and you will receive a Notice of Reassessment for the respective year(s).

@jimcar 

No. I can't find the box to choose Request for Net Capital Loss Carry Back. Losses under Form Lookup gives me a choice for S3 or Loss Worksheet. Where is the box?

• Select Find and enter losses in the search bar
• Select Losses from the search results, then Go
• Select the Request for Loss Carryback box
• Select Continue until you reach the Net Capital Loss Carrybacks screen
• The maximum net capital loss that you can carry back is listed. Enter the amount(s) you wish to carry back for each applicable year, then select Continue

Working in Forms mode in Turbotax Desktop, you'll instead lookup the T1A form, selecting "Request for Loss Carryback" from the list.

Your net capital loss available for carryback is found in Part 5, on line R, and below you will indicate the respective year adjustments.

@jimcar