we have considered cost allocation from a single support department to several producing departments. We used the direct method of support department cost allocation,in which support department costs are allocated only to producing departments. This was appropriate in the earlier example because on other support departments existed. This would also be appropriate when there is no possibility of interaction among support departments. Many companies do have multiple support departments and they frequently interact. For example, in a factory, Personnel and Cafeteria serve each other, other support departments, and the producing departments.
Ignoring these interactions and allocating support costs directly to producing departments may produce unfair and inaccrurate cost assignments. For example, Power, although a support department, may use 30 percent of the services of the Maintenance Department.