If you find that you have done any of the following, you should file an amended return 1) you did not report some income; 2) you claimed deductions or credits you should not have claimed; 3) you failed to claim some deductions or credits you are entitled to; or 4) you used an incorrect filing status. The form you use to correct the Form 1040 (PDF), Form 1040A (PDF), or Form 1040EZ (PDF), you already filed is Form 1040X (PDF), Amended U.S. Individual Income Tax Return. Please refer to Tax Topic 308, Amended Returns, for additional information.

References:

• Form 1040 (PDF), U.S. Individual Income Tax Return
• Form 1040A (PDF), U.S. Individual Income Tax Return
• Form 1040EZ (PDF), U.S. Individual Income Tax Return for Single and Joint Filers with No Dependents
• Form 1040X (PDF), Amended U.S. Individual Income Tax Return
• Tax Topic 301, When, where, and how to file
• Tax Topic 308, Amended Returns

Source: www.irs.gov