When dealing with taxes – as with everything else in life – people make mistakes. So, the IRS has made it possible to correct your mistakes if they’re made on your tax return.

If you discover an error after you’ve filed your tax return, you can correct it by filing an amended return. To help you decide if you need to amend your return, the IRS has published a helpful list of facts:

When should I amend a return? You should file an amended return if your filing status, dependents, total income or deductions/credits were reported incorrectly.
When should I NOT amend my return? If you made a math mistake in figuring your taxes or forgot to include a form (such as a W-2 or a schedule), the IRS usually corrects the math mistakes and will simply request the missing form from you. In this case, no amended return is necessary.
What form do I use to amend my return? You should use Form 1040X, Amended U.S. Individual Income Tax Return, to amend your filed Form 1040, 1040A or 1040EZ. Remember to check the box for the year of the return you’re amending on the 1040X. You’ll also have to mail in your amended return – they can’t be e-filed.
What if I’m amending more than one return? Prepare a 1040X for each return, and mail them in separate envelopes to the appropriate IRS processing center.
What do I need on Form 1040X? The form has three columns.

Column A shows original figures from the original return (if the return was previously amended or adjusted by the IRS, use the adjusted figures).

Column C shows the corrected figures. The difference between the two columns is shown in Column B.

You can explain the specific changes and the reason for the changes in an area on the back of the form.
What if I need other forms or schedules? If your changes require other schedules or forms, you can attach them to your 1040X.
What if I need to file to claim an additional refund? If filing to claim an additional refund, you should wait until you have received your original refund before filing Form 1040X. You can cash that check while waiting on your additional refund.
Should I use 1040X to pay additional tax? Yes. File your 1040X and pay the tax as soon as possible to limit interest and penalty charges.
How long do I have to file an amended return? As a rule, you must file your 1040X within three years from the date you filed your return, or two years from the date you paid the tax, whichever is later.
How long does it take to get an amended return processed? Normally, amended returns will be processed in 8 to 12 weeks.

10 Facts About Amending your Tax Return