If the optional Group unit is turned on, then you can setup several  Group revenue/expense units within each Department.

AMS360 ships with the Group unit turned off. If you want to use this business unit, you must turn it on before any posting takes place in AMS360.

If the optional Group unit is turned off, then Departments are the last revenue/expense business unit available to your agency.

Study your agency structure carefully before making the decision to turn on the Group business unit.