File an amended return using Form 1040-X if you made a mistake on your original tax return

An amended tax return is a corrected version of a tax return you already filed. You use it to report income you missed, claim deductions or credits you forgot, or fix errors in numbers or filing status. The IRS form is called Form 1040-X, and you file it separately from your original return — you do not resubmit the whole return.

You can file an amended return up to three years after the original due date (or three years from when you filed it, whichever is later). If you owe money as a result of the amendment, you will owe interest and possibly penalties from the original due date. If the amendment means you overpaid, the IRS will refund the difference or let you apply it to next year's taxes.

Key Takeaways

  • File Form 1040-X to correct mistakes on a return you already submitted; do not file a new Form 1040.
  • You have three years from the original due date to file an amended return and claim a refund.
  • The IRS processes amended returns more slowly than original returns — expect four to six months for a refund.
  • If you owe money because of the amendment, interest accrues from the original due date, not from when you file the corrected return.
  • Attach supporting documents and a clear explanation of what changed and why.

When you need to file an amended return

File an amended return if you reported the wrong income, missed a deduction or credit, used the wrong filing status, or made a math error. Common reasons include forgetting to report a 1099 form from a second job or side income, missing a dependent, claiming the wrong number of withholding allowances, or discovering you were may have access to to a credit you did not claim.

You do not need to amend if the IRS already caught the error and sent you a notice. In that case, respond to the notice instead. You also do not need to amend for a small math error if the IRS has not contacted you and the error does not change your refund or balance owed by more than a few dollars — though it is safer to correct it anyway.

How to get Form 1040-X and what to include

Download Form 1040-X from IRS.gov or request it by mail. The form has three columns: your original amounts, the corrections, and the new totals. You fill in only the lines that changed — you do not need to rewrite your entire return.

On the form, explain what you are correcting in the space provided. Be specific: "Added W-2 from ABC Company, $45,000" is clearer than "Correction to income." Attach copies of any new documents that support the change — a 1099 you did not include before, a receipt for a deduction, proof of a dependent, or a corrected W-2 from your employer.

If you are amending because your employer sent you a corrected W-2 (a W-2c), attach a copy of that form. If you are claiming a credit you missed, attach the form that documents it — for example, Form 8863 for education credits or Form 2441 for child care expenses.

Where to send your amended return

Mail Form 1040-X to the address listed in the instructions for that form — it varies by state and filing status. Do not file it electronically through tax software; the IRS does not accept e-filed amended returns for most taxpayers. Use certified mail with return receipt if you want proof the IRS received it.

Include a check if you owe money. Make it payable to "United States Treasury" and write your Social Security number and "1040-X" on the memo line. If you are owed a refund, the IRS will send it by mail or deposit it to the account you specify on the form.

How long the IRS takes to process an amended return

The IRS typically takes four to six months to process an amended return, sometimes longer. This is much slower than processing an original return. You can check the status using the IRS's "Where's My Amended Return?" tool on IRS.gov after you have waited three weeks from the date you mailed it.

Do not file a second amended return if the first one is still being processed. Wait for the IRS to finish. If you discover another error while the first amendment is pending, you can file a second amendment after the first one is complete, but this slows things down further.

Interest and penalties on amended returns

If your amendment means you owe additional tax, the IRS charges interest on that amount from the original due date of the return, not from when you file the amendment. The interest rate changes quarterly and is set by the IRS. You will also owe a failure-to-pay penalty if you do not pay the additional tax by the original due date, though the penalty is usually small if you pay when you file the amendment.

If you amended because you missed income or a deduction, you may also owe an accuracy-related penalty of 20 percent of the underpayment, depending on the circumstances. The IRS will calculate this and include it in the notice they send you.

What happens after the IRS processes your amendment

The IRS will send you a notice showing the results of the amendment. If they approved it and you are owed a refund, the refund will arrive by mail or direct deposit. If they denied part of it or found an error, the notice will explain why and what you owe or are owed.

If you disagree with the IRS's decision on your amendment, you have the right to appeal. The notice will include instructions for how to do that. You can also contact the IRS directly if you have questions about the processing, though wait times are long.

Frequently Asked Questions

Can I file an amended return if I have not filed my original return yet?

No. File your original return first, then file the amended return afterward. If you have not filed yet and the deadline has passed, file the original return as soon as possible to minimize penalties, then file the amendment if needed.

Do I need to amend if I forgot to report a small amount of income?

Yes, if the amount is more than a few dollars. The IRS will likely catch unreported income when it matches your return against 1099s and W-2s sent by employers and financial institutions. It is better to correct it yourself than wait for the IRS to contact you, because you will owe penalties and interest either way, but correcting it yourself shows good faith.

What if I made a mistake on an amended return I already filed?

You can file another amended return to correct the second mistake. Wait for the IRS to finish processing the first amendment before you file the second one. You can file multiple amendments if needed, though each one takes several months to process.

Can I file an amended return for a year that is more than three years old?

No. The IRS will not process an amended return filed more than three years after the original due date. If you discover an error after that deadline, you cannot claim a refund, though you may still owe additional tax if the error was in your favor.

Should I file an amended return if the IRS already sent me a notice about the error?

No. Respond to the IRS notice instead of filing an amended return. The notice will tell you what to do and whether you owe money or are owed a refund. Filing an amendment after receiving a notice can confuse the IRS's records.