What Is Form 1040X: Amended U.S. Individual Income Tax Return?

Form 1040X: Amended U.S. Individual Income Tax Return is issued by the Internal Revenue Service (IRS) to taxpayers who need to amend their tax returns for any reason. Form 1040X is necessary for an amended tax return that will change tax calculations, such as changes to filing status, number of dependents, or corrections to income credits or deductions. However, it’s important to avoid using Form 1040X for mathematical errors in your tax return, as the IRS will correct any in your return.

This form should be filed by anyone who has already filed a tax return and would like to do the following:

  • Correct Forms 1040, 1040-A, 1040-EZ, 1040-NR, or 1040-NR EZ.
  • Make elections after the prescribed deadline.
  • Change any amounts previously adjusted by the IRS.
  • Make a claim for a carryback due to a loss or unused credit.

In order to receive a credit, taxpayers must file Form 1040X within three years after the original return was filed or within two years after the tax was paid, whichever is later.

Key Takeaways

  • Form 1040X is filed by taxpayers who need to amend their tax returns.
  • The form must be filed within three years after the original return was filed or within two years after the tax was paid, whichever is later.
  • Anyone who files Form 1040X may also need to amend their state tax return.

Special Considerations for Form 1040X: Amended U.S. Individual Income Tax Return

This form is an itemized, line-by-line description of all necessary adjustments, so the taxpayer can clearly record the exact type and amount of each amendment and give a brief description of what is being amended and why.

Form 1040X Part III is where the filer can explain the changes being made to a previously filed tax return. 

The IRS provides the following tips to taxpayers about Form 1040X:

  • Wait for the first refund. If your original tax return included a refund, you should wait until you receive it before filing Form 1040X. The IRS will issue a separate, second refund if it is warranted, so you are free to cash the first check.
  • File Form 1040X within the three-year amendment time period. If your change will affect your refund amount, you must file the form within three years from the date of your original tax return or within two years from the date of paying the tax amount, whichever is later. Any returns filed early will be considered filed on the official due date of tax season, generally April 15 of the calendar year.

The IRS requires the filer to provide a copy of the return being amended as well as any notices about adjustments to that return. The Form 1040X: Amended U.S. Individual Income Tax Return can be downloaded here.