You should file a Form 1040X, Amended U.S. Individual Income Tax Return, if you made an error claiming your filing status, income, deductions or credits on your original return.

You usually have three years from the date you filed your original tax return to file Form 1040X to claim a refund. You can file it within two years from the date you paid the tax, if that date is later. That means the last day for most people to file a 2017 claim for a refund is April 15, 2021.

There is no time limit on filing an amended return to include additional income or correct overstated deductions, or other changes that will not result in a credit.