Absent a pandemic or other reasons for IRS furlough, Mail-in audits are usually commenced within seven months of the filing of the tax document. They often take 3-6 months to complete. Field audits are usually commenced within a year after you file a return and are usually completed within 3-6 months. Typically, the IRS only has three years from the date you filed the return or that it was due (whichever is later) to complete the audit.