It depends on the type of mistake you made:

• Many mathematical errors are caught during the processing of the tax return and corrected by the IRS, so you may not need to correct these mistakes.
• If you didn't claim the correct filing status or you need to change your income, deductions, or credits, you should file an amended or corrected return using Form 1040-X, Amended U.S. Individual Income Tax Return.

When filing an amended or corrected return:

• Include copies of any forms and/or schedules that you're changing or didn't include with your original return.
• To avoid delays, file Form 1040-X only after you've filed your original return. Generally, for a credit or refund, you must file Form 1040-X within 3 years after the date you filed your original return or within 2 years after the date you paid the tax, whichever is later.
• If you file an amended or corrected return before the due date for the original return, the amended return will replace or supersede the original return. Filing a superseding return and paying any additional taxes owed may allow you to avoid interests or penalties.
• Allow 8 to 12 weeks for your amended return to be processed; however, in some cases, processing can take up to 16 weeks. For current processing status, check our processing status dashboard.