If you find errors or left out information on your original return, file Form 1040X. This is the Amended U.S. Individual Income Tax Return. By filing an amended return:

• You might receive an additional refund.
• You might owe additional taxes as a result of the correction.

If you're due a refund, the IRS will send it to you after it accepts your amended return. If you owe tax, send the amount owed to the IRS along with Form 1040X. If interest or a penalty is due, the IRS will bill you.

Ex: In June 2013, you discover that you didn't include on your 2012 return the $500 dishwasher (fair market value) you won on a game show. File Form 1040X for 2012 to include the $500 value in your income.

When you file a Form 1040X, attach these items if required to support changes on your amended return:

• Forms
• Schedules
• Statements

Ex: You originally filed Form 1040A. When you found you hadn't reported all your income, you also discovered that itemizing deductions would reduce your tax liability. You can claim your itemized deductions on Form 1040X. However, you also must complete Schedule A and attach it to the 1040X.

When you amend a return for a specific reason, it's a good idea to review your entire original return. Look for deductions, credits, and exemptions that you might have missed the first time around.

Also, review the filing status you used on your original return. You might be eligible for the head of household or qualifying widow(er) filing status. Both of those can save you considerable tax dollars.

Due Date for Filing Form 1040X

You usually must file an amended return by the later of these dates:

• Within 3 years from the date you filed your original return
• Within 2 years from the date you paid the tax

If you filed your return on or before the filing deadline, the filing deadline is considered the filing date. If you received an extension, the filing date is 1 of these:

• Actual date you filed your return within the extension period
• Filing deadline if you filed your return after the extension period expired

Ex: You’re amending your 2012 return, which you filed on April 2, 2013. Since the IRS considers the date you filed to be April 15, 2013, you have until April 15, 2014, to file an amended return.

If you're amending your return because of a bad debt or a worthless security, you have 7 years after your original return’s due date to file the amended return.

You can also file an amended return after 3 years for a year when you carried a net operating loss (NOL). You must file the amended return within 3 years of the due date of the return for the year when the NOL arose.

Ex: An NOL arose in tax year 2011, and you carried it back to tax year 2009. You can file an amended return for the 2009 tax year up until April 15, 2014.

The IRS usually has 3 years to assess additional taxes. However, longer periods apply for significant underreporting of income or fraud.

Completing Form 1040X

To file an amended return, download and file Form 1040X from www.irs.gov. You must mail this form. It can't be e-filed.