In general, employers are responsible for the actions of their employees. This is respondeat superior, or the master-servant relationship, a term that dates the origins of the concept. More generally, liability for actions of others is called vicarious liability. MCOs are responsible for the actions of both physician and NPP employees. As discussed above, this responsibility is not affected by ERISA. Physicians who employ NPPs and others in their own offices will also be vicariously liable for their employees’ actions, as long as these actions are in the course and scope of their employment. This rule poses two questions, Who is an employee? And what is the course and scope of employment?

Although it is commonly assumed that employment status is determined by how a person is paid, this is only one of several factors that are considered. Even unpaid volunteer workers may be classified as employees for the purpose of vicarious liability. The usual focus is on payment because most disputes about employment status involve the tax laws rather than the tort laws. The whole work situation is considered when determining whether there is vicarious liability for a person’s actions.