How do i claim capital losses from past years. I think there is a limit of 3k per year.

If you still have a capital loss carryover for 2024, you can enter it as follows (click the link):

• How do I enter my capital loss carryover? 
  • This will come from your carryover worksheet in the 2023 tax return (see the worksheet with Schedule D).
  • 2023 Instruction 1040 (Schedule D), page D-11

Limit on the Deduction and Carryover of Losses

If your capital losses exceed your capital gains, the amount of the excess loss that you can claim to lower your income is the lesser of $3,000 ($1,500 if married filing separately) or your total net loss shown on line 16 of Schedule D (Form 1040). Claim the loss on line 7 of your Form 1040 or Form 1040-SR. If your net capital loss is more than this limit, you can carry the loss forward to later years. You may use the Capital Loss Carryover Worksheet found in Publication 550, Investment Income and Expenses or in the Instructions for Schedule D (Form 1040) to figure the amount you can carry forward.

If you do need to amend any prior year tax return that should have had a capital loss carryover see the information below and complete this before you add the loss to 2024.  You don't have to wait to file the 2024 return but you do want the correct numbers.

• For tax years 2023, 2022, or 2021 - How do I file my 2023, 2022 or 2021 Tax Return?