IRS Form 1040-X

Form 1040-X: Amended U.S. Individual Income Tax Return

A plain-English guide to IRS Form 1040-X — what it's for, who files it, when it's due, and how to complete it.

Form number1040-X
Official nameAmended U.S. Individual Income Tax Return
CategoryIndividual
Typically dueWithin 3 years of filing
Official IRS Form 1040-X (PDF)

What is Form 1040-X?

Form 1040-X corrects a return you already filed — to fix income, add a missed deduction or credit, or change your filing status.

A 1040-X is built around three columns: what you originally reported, the change, and the corrected figure, plus a short written explanation. You generally have three years from the original due date to amend and still collect a refund, so there's rarely a reason to rush a same-week correction.

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Who files it

Anyone who needs to correct a previously filed Form 1040.

When it's due

Form 1040-X is generally due Within 3 years of filing. Deadlines can move for weekends and holidays, so confirm the exact date for the current year on IRS.gov.

Key lines and parts

Here's what you'll actually fill in on Form 1040-X:

  • Column A — original amounts
  • Column B — net change
  • Column C — corrected amounts
  • Part II — explanation of changes

How to file

Show the original figures, the changes and the corrected amounts, and explain why. Many amended returns can now be filed electronically.

Common mistakes & penalties

Don't amend for arithmetic slips or a missing form the IRS can add itself — they'll often fix those and send a notice. Amend when the substance was wrong: unreported income, a missed deduction or credit, or the wrong filing status. And if the change affects your state return, amend that too.
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Frequently asked questions

What is IRS Form 1040-X?

Form 1040-X corrects a return you already filed — to fix income, add a missed deduction or credit, or change your filing status.

Who has to file Form 1040-X?

Anyone who needs to correct a previously filed Form 1040.

When is Form 1040-X due?

Form 1040-X is generally due Within 3 years of filing. Always confirm the current year's date on IRS.gov, since deadlines shift for weekends and holidays.

What's the most common mistake with Form 1040-X?

Don't amend for arithmetic slips or a missing form the IRS can add itself — they'll often fix those and send a notice. Amend when the substance was wrong: unreported income, a missed deduction or credit, or the wrong filing status. And if the change affects your state return, amend that too.