High risk category
The highest risk of audit is born by the President of the Unites States who is automatically audited by the IRS every year. President Trump says this is very unfair. But what about the rest of us?
Any taxpayer who omits an income item filed by a third party (a W2 form by an employer or a bank interest filing, for example) faces a high chance of correspondence audit. These are computer-generated exams based on mis-matching data.
A marijuana related business. The frequency of severe audit outcomes compares to the number of businesses in this category is shockingly high. More disturbing is the size of the judgements, the number of resulting bankruptcies and even on high profile suicide of a tax case loser.
Medium risk category
High income earners and self-employed people who take unusual deductions are audited more frequently but audit rates may depend on the specific situation.
People who file tax returns showing zero income face a 1 in 20 risk of audit.
Low risk category
All other taxpayers face less than 1 in 100 audit risk.