This greatly depends on the type of mistake you made. Many mathematical errors are caught by the IRS during the processing of the tax return. The IRS will mail you a notice to inform you of the change. If, however, you claimed an incorrect status or need to make a change of dependents or deductions, you need to file an amended tax return. The amended return can be filed within three years of the original filing. If the change causes you to owe more tax to the IRS, there will be interest and potentially penalties also.
If you have other questions about mistakes on filed tax returns or the preparation of your tax return call the Tax professionals at Ketel Thorstenson today, 605-342-5630.