What is Form 1040X

Form 1040X is a form used by taxpayers who have to amend their tax returns for any reason. Form 1040X is an itemized, line-by-line description of all necessary adjustments, so that 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 can be downloaded off the Internal Revenue Service website. According to the IRS website, even the government understands that mistakes happen, which is why the form exists in the first place. However, they note that it’s important to avoid using Form 1040X for mathematic errors in your tax return; the IRS is full of experts who will correct any mathematical errors in your return. Form 1040X, on the other hand, is necessary for amendments to your tax return that will change tax calculation, such as changes to filing status, number of dependents, or corrections to income credits or deductions.

In most cases, taxpayers who use this form need to also amend their state tax returns. Taxpayers must fill out this form regardless of whether they initially used Form 1040, Form 1040A or Form 1040EZ.

Tips for Filing Form 1040X

The IRS offers several tips for filing a Form 1040X, not the least of which is to ensure that you never file the form at the request of the IRS contacting you via social media or a text message, as those are common scam techniques. The IRS will only contact you through an official letter in the mail and you can check your account online to confirm any claims that you owe the IRS money. Additional tips include to:

  • Wait for the first refund. If your original tax return included a refund, you should wait until that is received 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.