What happens when you realize you made an error on your tax return? Most people think they should file an amended tax return, and in most cases that would be correct; however, sometimes it is unnecessary. According to the Internal Revenue Service, if you made a math error, the IRS will correct it for you; an amended return is not normally required. Or, if you forgot to attach a tax form such as a W-2, you do not need to amend your tax return; the IRS will contact you and request missing forms if necessary. If you are due a refund based on your return as originally filed, the IRS recommends waiting to receive the refund before filing an amended return to claim an additional refund. If you are amending multiple years, you should mail them in separate envelopes, and finally, you should always amend your return if you made an error regarding your filing status, income, deductions or credits on your original tax return.