What Is IRS Form 1040-X?

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Form 1040-X is an amended tax return for individuals. It corrects, deletes, or adds information to a Form 1040 return that's already been filed with the IRS. You might find it necessary to file Form 1040-X if a new W-2 or 1099 arrives for income that you'd forgotten about, or if your ex tells you that she also claimed your child as a dependent.

What Is Form 1040-X?

Form 1040-X effectively replaces a Form 1040 that contained errors. It allows you to set things right with the IRS, but it doesn't just include the changed information. The correct information from your previous return must be transferred from your Form 1040 to Form 1040-X as well.

File amended tax return Form 1040-X if the information you're correcting will alter the tax calculations on your original return. Do not file an amended return to correct math errors. The IRS computers will check your math and correct any errors in calculation. Form 1040-X is for use solely if you entered any erroneous information on your previous return or overlooked something.

IRS Form 1040-X

Types of Form 1040-X

There's only one Form 1040-X, but it's undergone some minor changes because the 1040 tax return changed significantly beginning with tax year 2018. The revised Form 1040 replaced Form 1040-A and 1040-EZ tax returns in that year. They're no longer available.

Form 1040-X was revised in July 2021 and this version should be used for the 2019 tax year and later years. You'll have to submit separate Forms 1040-X for each year if you want to revise several tax returns. 

Where to Get Form 1040-X

Form 1040-X is available on the IRS website. You can print out a copy and fill it out by hand, or you can enter your information into the interactive form and then save and print out a completed version.

Most reputable tax software also prepares amended returns.

How to Fill Out and Read Form 1040-X

Make sure you have both your original tax return and Form 1040-X in front of you when you begin making changes because Form 1040-X basically summarizes the information you're changing. Each section of the form is clearly marked as to what information you should enter and where.

  • Indicate the tax year of the return you're amending at the top of the first page of Form 1040-X.
  • Make changes to your reported income and to tax deductions you claimed on page 1, lines 1 through 5, "Income and Deductions." You can amend your above-the-line deductions here, your standard deduction, or itemized deductions.
  • Enter corrected information about your dependents in Part I on page 2, lines 24 through 30. This is the appropriate section if you initially entered a wrong Social Security number for one of them, if you want to drop one or more dependents, or if you want to add one or more.
  • You can claim additional tax credits that you missed when you filed your original return on page 1 as well, or remove tax credits mistakenly taken or recalculate the amount of the credits. This information is entered under "Payments," lines 12 through 17, because credits effectively act as payment of any tax obligation you owe.
  • Calculations for your refund or the amount you owe the IRS go on lines 18 through 23 on the first page of Form 1040-X. You'll have to reimburse the IRS if you received a larger refund from your original tax return than you should have. Enclose a check for the difference to avoid interest and penalties. Do not staple or otherwise attach the check to your Form 1040-X.

The most important part of Form 1040-X is probably Part III, on the second page. This is where you can explain the changes you're making to your previous tax return.

Your Part III explanation might read like this if you forgot to include wages from a W-2 on your original return:

"I am reporting additional wages and additional withholding from a W-2 that weren't included on my previous tax return. This resulted in changes to my adjusted gross income, taxable income, total tax, and my refund."

Try to be as concise as possible. Point the IRS to the specific changes you're making, and tell them where they can find proof of those revisions in your supporting documentation.

Can Form 1040-X Be E-Filed?

The IRS announced in August 2020 that it would begin accepting e-filed Forms 1040-X.

Where to Mail Form 1040-X

You can mail your amended return to the same IRS Service Center that processed your original tax return if you prefer to send in a paper copy. The IRS also provides a comprehensive list of mailing addresses on its website for various circumstances that require filing an amended return and depending on your state.

Be sure to include any and all schedules that you've changed, and any new Forms W-2 or 1099 that represent changes from the information you filed with your original return. Attach the W-2s or 1099s to the front of Form 1040-X if you're mailing in a paper copy.

Requirements for Filing Form 1040-X

You have three years to make any corrections that will result in a tax refund or an additional refund. That's the IRS statute of limitations on issuing refunds. This three-year period begins on the return's due date, which is usually April 15, if you filed your original return on or before that date. But it runs from the date you filed if you filed later than April 15, such as because you requested an extension.

You can only receive refunds for overpaid taxes that were paid during the previous two years if you're beyond this three-year period. You can't collect any refundable tax credits you might have missed claiming when you filed your original return if you wait too long.

Taxpayers who want to report additional income or correct overstated deductions can file an amended return at any time. The IRS also has three years to audit your tax return, and it might have still more time if there's been substantial under-reporting of income.

After You File Form 1040-X

The IRS Service Center will make sure your explanations are sufficient and that you've documented the changes you made to your tax return. You'll receive a letter asking for any specific information needed if the IRS requires more explanation or additional documentation.

The IRS scrutinizes amended tax returns a little more carefully during processing, so take extra care to make sure your Form 1040-X is as complete and accurate as possible. The IRS is likely to process your amended return without fuss if you clearly explain why you're correcting your tax return and if you back it up with proper documentation.

The IRS agent can look up corroborating information on the IRS computer, but it will be easier and more efficient if they can see the documentation right there with your amended tax return.

There's no conclusive evidence that an amended tax return will trigger an audit. The IRS uses the same screening process for Forms 1040-X that it uses for regular returns.  

Key Takeaways

  • Form 1040-X is an amended tax return that allows you to correct a previous return on which you made mistakes.
  • You can correct virtually any inaccurate information on Form 1040-X, from your claimed dependents to income you reported and deductions and credits you previously claimed.
  • The form provides a dedicated section where you can explain what you’re changing and why.
  • You have three years to file Form 1040-X if the changes you're making will result in a refund or an increased refund.

Article Sources

  1. Internal Revenue Service. "Amended Returns & Form 1040X."

  2. Internal Revenue Service. "Here Are Five Facts About the New Form 1040."

  3. Internal Revenue Service. "Now Available: IRS Form 1040-X Electronic Filing."

  4. Internal Revenue Service. "Topic No. 308 Amended Returns."

  5. Internal Revenue Service. "IRS Audits."