How do I file an amended tax return?

When and How to File an Amended Tax Return

Amended Tax Return
••• Credit: teekid | Getty Images

Taxes are confusing enough, but what if you discover you've made an error? Maybe you filed early and later discovered you understated your income, miscalculated your credits, or received a revised 1099 Misc or other income statement. 

First, don't panic. While most tax experts recommend sending amended return, odds are the IRS will catch the error and contact you about fixing it. 

Second, here are somethings you should know about filing an amended tax return.

When You Should File an Amended Tax Return

You don't need to file if you made a math error or forgot to attach your tax forms (i.e. W-2). The IRS will contact you about these issues. However, if your filing status, your income, your deductions or your credits were in error, or something that significantly changes your tax liability, you ARE required to file and amended tax return using Form 1040X.

Why might these issues happen? It could be a significant miscalculation on your part, especially if you file early. Sometimes its because you didn't receive your 1099 Miscs on time or received an revised 1099. 

How to File an Amended Tax Return

The amended tax return is just another tax form to fill out. The difference is that you can only file by mail (no e-filing), and you have three years from the original filing to submit your amended return. You can use Form 1040X to amend a previously filed:

  • Form 1040
  • Form 1040A
  • Form 1040EZ
  • Form 1040NR (PDF), or
  • Form 1040NR-EZ

Form 1040X has three columns:

  • Column A is where you input your original figures
  • Column B is the difference between Columns A and C.
  • Column C is where you put the corrected figures.

On the back of 1040X there is space to explain the changes and why you're making them. 

Some points you'll want to keep in mind:

  • If you are filing to claim an additional refund, wait until you get the original refund (go ahead and cash the check).
  • If you owe additional tax, file Form 1040X and pay the tax by April 15 of the following year (or the next business day if April 15th happens to fall on a weekend or a legal holiday). The Form 1040X Instructions list the addresses for the service centers where your amended return needs to be sent.
  • Be sure to indicate the year of the return you are amending on the front of Form 1040X.
  • File a separate Form 1040X for each year you are amending. Mail each form in a separate envelope.
  • If your amended return includes changes to other schedules or forms (i.e. Schedule C), you must attach it to the amended return. You need to include any new W-2s as well. 
  • Note that your state tax liability may be affected by changes made on your federal return, so you'll need to contact your state's tax agency on how to amend your state return. The IRS provides links for every state website.
  • Fix ALL errors, not just the ones that benefit you. There's much folklore around what might trigger an audit, sending an amended return is one of them. So make sure it's correct. 
  • You do not need to attach newly received or corrected 1099-MISCs as you were not required to attach them to your original return. Employers are required to file informational copies of 1099s direct to the IRS.

The IRS says that normal processing time for Form 1040X is 8 to 12 weeks from the date they receive it. You can follow up on the status of your form using the IRS's service, Where's My Amended Return? (WMAR) online tool or call the toll-free telephone number 866-464-2050. Give the IRS at least three weeks before contacting it about your amended return. 

Updated June 2016 Leslie Truex