The internal revenue service pays careful attention to whether an employer has properly classified its workers as independent contractors or employees.  As important as the question is, there is no simple answer.  In fact, the IRS' training materials on the subject, which it uses to train its examiners runs a mere 160  pages.

There are however, some  general guidelines that every employer can and should follow in order to avoid incorrectly classifying its workers.

Read the entire article on classifying independent contractors.