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 did not attach a required schedule or form, the IRS will contact you and ask for the missing information.
• If you did not claim the correct filing status or you need to change your income, deductions, or credits, you should file an amended or corrected return.