How long can you claim a stock loss?

After you complete your schedule D of the 1040 income tax with gains and losses offsetting each other and after that any remaining carryover loss is used up to 3000 limit to offset up to 3000 of ordinary income on page 1 of 1040 tax form each year until the carryover loss amount is used up.

And each year you have to use the carryover worksheet to determine the remaining amount of carryover loss to the next year.