Like correcting a bank deposit slip after noticing a missing number, an amended return is a revised tax return filed to fix a return that was already sent in. For federal taxes in the United States, individuals usually do this with IRS Form 1040-X to correct income, filing status, deductions, credits, or other items that were reported incorrectly or left out. An amended return does not replace every prior filing automatically; it identifies what changed and why, and it can lead to an additional refund, more tax due, or no change at all.

Practically, an amended return can matter when an error would otherwise trigger penalties, interest, or an audit, or when a taxpayer realizes they missed a deduction or credit. Under IRS rules, a claim for refund on an amended return generally