IRS Link to Form — Found Here
Form 1040-X is the amendment form used to change previously submitted information from the 1040, 1040-A, or 1040-EZ tax filing form.
The taxpayer has 3 years to file the 1040-X to make changes. The 1040-A and EZ are simpler versions of the 1040 which can be used by individuals who have relatively simple filings to do, and have modest household income.
The 1040-X requires a line-by-line amendment request and explanation of why the changes are being requested. You will also need to attach supporting documents that provide more information about the changes being requested.
Common reasons are for a self employed individual to carry-back and net operating loss (NOL), to claim a tax credit or deduction for something that you didn’t realize was eligible, or to change a filing status to head of household or married filing jointly if you have discovered that it would be more advantageous to you.