The IRS conducts audits for a variety of reasons. An audit may be random, based on a tip (such as from an ex-business partner or spouse), or be conducted pursuant to a special program, such as audits of high net worth individuals. However, the most common reason to be audited is due to red flags being raised by a computer program used by the IRS that determines the likelihood that a particular tax return has errors. This program determines a Discriminant Index Function (DIF) score, which is an indication of the probability that your tax return has errors. A high DIF score may be triggered by things like claiming unreimbursed business expenses that exceed your income.