8.2.1 Allocating Overheads
We can look at overhead costs (or indirect costs) as being incurred while providing a service to the process that produces the output. In a business with a single line product or service all the overheads are incurred in providing a service to the output process. In a business with multi-product or service lines we must decide how much of the service provided by the overheads is used by each line of product or service output. Once we work out a split of the services provided by the overheads we can apportion the cost.
So the problem is to find a basis or measure by which the amount of services provided by the overheads is used by each kind of output. This basis must be observable and in some way measurable. One way to do this is to share out the overheads equally over the units of output, and we can do this if the outputs get the identical benefit from the overheads.
In practice, a commonly used method is based on direct labour hours (DLH). The logic is that a product or service output that requires more direct labour hours is using more of the services from the overheads. Also many overheads relate to time. For example, the expenses related to rent, lighting, heating, manager's salaries and other overheads for a week will be close to half the amount for two weeks and so on. Direct labour hours are easily measured and can be related directly to each job. This information is already collected to calculate the direct labour cost for each job.
There isn't a single 'correct' way to allocate overheads. By definition overheads don't relate directly to a job, so the best we can do is find a basis that seems logical or fair. As we want to give useful information to decision makers any method that gives 'acceptable' results is an acceptable method.
The next reading gives a good example of direct labour hours compared with direct machine hours. It goes on to discuss segmenting overheads and dealing with them on a departmental basis. It is a key reading.
Text reading
Atrill, Mclaney, Harvey & Jenner, pages 270-272.
Read these pages again and work through Examples 8.1 and 8.2 and do Activity 8.5