The IRS has just recently published statistics on the number of audits it performs and which taxpayers are more or less likely to be audited.
In broad terms, a taxpayer making over $200,000 a year has about a 1 in 25 chance to be audited. If the taxpayer’s income is $1 million a year, then his chances of being audited go up to about 1 in 8. For those making under $200,000 a year, the chances of being audited are only about 1 return out of 100.