A taxpayer should file an amended tax return if that taxpayer needs to correct his or her filing status, total income, tax deductions, or tax credits. A taxpayer generally should not file an amended return to simply correct mathematical errors!
According to the IRS, the "Form 1040X" will be the taxpayer's new tax return, changing the original return to include new information. The entries that the taxpayer will make on Form 1040X under the columns headed Correct Amount and Correct Number or Amount are the entries the taxpayer made on the original tax return had it been done had it been done correctly.
To complete Form 1040X, the taxpayer will need the following;
1. A copy of the tax return that is being amended including supporting forms, schedules, and any worksheets that were completed;
2. Any Notices from the IRS on any adjustments to that tax return.
To access additional information, please click the IRS website page at http://www.irs.gov/pub/irs-pdf/i1040x.pdf