The 20-factor test is used as an aid by the IRS to determine whether an employment relationship exists between the individual and the firm under common law rules, for federal employment tax purposes. The factors are applied to the given factual situations to determine whether the individual is an employee of the firm for such purposes.
These factors have been developed based on an examination of cases and rulings considering whether an individual is an employee. As Edward E. Lenz highlights in his book Co-Employment, “the degree of importance of each factor varies depending on the occupation and the factual context in which the services are performed.”