1. When to use Form 1040X

You can file Form 1040X to amend a previously filed tax return that used one of these forms:

You will be able to correct any mistakes, including:

  • Filing status
  • Exemptions
  • Income
  • Deductions or credits

Don’t worry about knowing tax rules. With TurboTax Live, you can connect with real tax experts or CPAs to help with your taxes — or even do them for you. Get unlimited tax advice right on your screen from live tax experts as you do your taxes, or have everything done for you—start to finish. So you can increase your tax knowledge and understanding and be 100% confident your return is done right, guaranteed

2. Not all mistakes require an amended return

You do not need to file a 1040X if your original return contains math errors or is simply missing forms, such as a W-2. The IRS will usually correct and notify you about math errors and will notify you if it's missing any forms.

3. Amended return timing

If the correction results in you owing money, file as soon as possible so you can minimize any penalties or interest that might be incurred. Although the IRS appreciates when taxpayers file an amended return to correct a mistake, they can still assess a penalty or charge interest for not paying the proper amount when the taxes were originally due.

If the correction results in a tax refund and you haven't received it yet, wait to file the amended return until after you've received it to avoid complications. But keep in mind that there is a time limit for filing an amended return resulting in a refund. You must file it within three years after you filed the original return, or within two years after you paid any tax due from that return—whichever is later.

Get every deduction you deserve. With TurboTax Deluxe, we'll search over 350 tax deductions and credits so you get your maximum refund, guaranteed. It’s free to start, and enjoy $10 off TurboTax Deluxe when you file. 

4. Preparing an amended return

To complete a Form 1040X, you'll need:

TheStreet Recommends

  • A copy of the original tax return that's being amended
  • W-2s
  • Schedules
  • Worksheets
  • Corrected information and calculations
  • Any forms needed to support corrections

However, you should not include the original return with the 1040X.

Note: Beginning in 2020 you can file a 1040X electronically but only for the tax year 2019 and later. For earlier tax years an amended returns have to be filed on paper.

5. Stating the reason for the amended return

Form 1040X, Part III, asks you to explain in your own words why you are amending the return. This explanation should describe the specific corrections you're making and can be very brief. Reasons might include:

6. But now I owe money

If you owe money as a result of the correction, you should include a check or money order with your 1040X submission. You can pay the balance you owe online, using Direct Pay or the Electronic Federal Tax Payment System (EFTPS). If you can't pay right now, file the amended return and apply for an IRS Installment Plan.

7. Mailing instructions for paper-filed amended returns

Each tax return you are amending requires its own Form 1040X mailed in a separate envelope. Mail the completed form to the appropriate address listed in the instructions on Form 1040X.

8. After you mail the 1040X

It takes about 16 weeks for the IRS to process an amended return. You can check its status on the IRS website after three weeks, or by calling the automated toll-free number 866-464-2050.

9. Check the status of your amended return

Use the IRS's new tool Where's My Amended Return to check on the status of your Form 1040X.

10. Amending your state tax return

After submitting Form 1040X, check to see if your state tax form also needs to be amended. If so, obtain the proper form from your state's tax agency and use the information on the federal 1040X to help you fill it out. Be sure to attach a copy of your 1040X to your state amended return.