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. The maintenance costs caused by Power Department belong to the Power Department. By not assigning these costs to the Power Department, its costs are understated. In effect, some of the costs caused by Power are hidden in the Maintenance Department because maintenance cost would be lower if the Power Department did not exist. As a result, a producing department that is a heavy user of power and average or below-average user of maintenance may then receive, under the direct method, a cost allocation that is understated.