A) According to the IRS: It depends on the type of mistake that you made:
- Many mathematical errors are caught in the processing of the tax return itself so you may not need to correct these mistakes.
- If you did not attach a required schedule, the IRS will contact you and ask for the missing information.
- If you did not report all of your income or did not claim a credit, you should file an amended or corrected return using Form 1040X(PDF), Amended U.S. Individual Income Tax Return.
When filing an amended or corrected return:
- Include copies of any schedules that have been changed or any Form(s) W-2 (PDF) you did not include. File 1040X only after you have filed your original return. Generally, for a credit or refund, you must file Form 1040X within 3 years (including extensions) after the date you timely filed your original return or within 2 years after the date you paid the tax, whichever is later.
- Please allow the IRS 8-12 weeks to process an amended return.
SEE Additional Information:
- Tax Topic 308, Amended Returns
- Instructions for Form 1040X (PDF), Amended U.S. Individual Income Tax Return