Not all filing mistakes involve broad interpretations; some tiny errors can still trigger that flashing, red "audit" light. One of the most common is overlooking out-of-state filing requirements. 

Complying with rules of states the taxpayer works in, has become a more frequent problem in the age of telecommuting when employees, or self-employed  may move to another state without leaving the company's employment. One can avoid trouble by making certain the IRS knows you are doing business in another state, even if it means no additional taxes; if you do not the IRS, or the state(s) might flag your return.