How do I amend a tax return?

File Form 1040-X (Amended U.S. Individual Income Tax Return) to correct a previously filed return. Since 2020, 1040-X can be e-filed for the most recent two or three tax years; older years require mailing a paper form. Include any corrected schedules or forms. The IRS typically processes amended returns in 16-20 weeks. If the amendment increases your refund, interest accrues in your favor; if you owe more, pay promptly to stop penalty accrual.