If you discover that you failed to report some income, you claimed deductions or credits you were not entitled to, you neglected to claim deductions or claims you are entitled to, or if you should have claimed a different filing status, you can file for an amended return. The form you use to amend a return is the 1040X (10-40-X). Also, you cannot file an amended tax return electronically; it must be mailed directly to the Internal Revenue Service Center serving your area. If you owe additional taxes, then you must pay the extra taxes, even if you expect a return. The IRS will not reduce the size of your refund check by a corresponding amount. In addition, you must file your claim for a credit or refund within three years after the date you filed your original return or within two years after the date you paid the tax, whichever is later. These notes are meant to be a general guide to federal income taxes. If you need specific advice, please consult a tax advisor or call the toll-free number for Federal Tax Information and Assistance at 1-800-829-1040.