First, you need to determine how much capital loss you have available. If you had no capital gains in any of the years since 2013, you must reduce the carryover by $3,000 for each year that has passed, since you were allowed to deduct that. If you had capital gains, you must reduce the carryover by the gains and $3,000 more. You can amend returns up to 3 years ago, but any years before that, the deduction is lost. Since you did not include the carryover on your return, you may be questioned by the IRS to prove you had a carryover, so keep your documentation handy.
To manually enter the capital loss carryover, navigate to Federal > Wages & Income > Investments and Savings > Capital Loss Carryover > Start or Revisit. You see a summary from the 2023 tax return, choose edit to adjust.
