Apart from the TCMP program, your return will be evaluated based on your “DIF” score,a set of IRS formulas known as the “Discriminate Function System.” About three-quarters of all returns audited are selected by the DIF computer, which compares deductions, credits, and exemptions with the norms for taxpayers in each income bracket.
While these formulas are kept very secret by the IRS, you can count on having a higher audit probability if you fall into certain categories or report certain things on your tax return.