Predetermined rates are used because overhead and production often are incurred
nonuniformly throughout the year, and it is not possible to wait until the end of the
year to calculate the actual overhead cost assignments (managers need unit product cost information throughout the year). A cost system that uses predetermined overhead rates
and actual costs for direct materials and direct labor is referred to as a normal cost system.
Budgeted overhead is simply the firm’s best estimate of the amount of overhead
(utilities, indirect labor, depreciation, etc.) to be incurred in the coming year. The estimate
is often based on last year’s figures, adjusted for anticipated changes in the coming
year. The second input requires that the predicted level for an activity driver be
specified. Assignment of overhead costs should follow, as nearly as possible, a causeand-
effect relationship. Drivers are simply causal factors that measure the consumption
of overhead by products. In functional-based costing, only unit-level drivers are used
to calculate overhead rates