Amendments are done in order to make corrections to a tax return from a previous year. An amended return can be used to correct errors and claim a more advantageous tax filing. For example, one might choose to file an amended return in instances of misreported earnings, tax credits or dependents. Mathematical errors, however, would not require amendments, as the IRS would automatically correct for such errors.
The applicable tax form required to file an amended return is Form 1040X. There is, however, a three-year statute of limitations on the filing of amended returns for the purpose of increasing a tax refund. An amended return filed to account for a return that resulted in underpaid taxes does not fall under any such statute.