8.1.2 Single product/service line
A simple example is a business that produces a single type of product or service. That is, it produces many of these but all products are identical or there is only one kind of service provided. In this situation we just add up all the costs incurred during a particular period and divide the total by the number of units of output for that period. There are some problems when working out costs such as wear and tear (depreciation), which is an estimate only and for which there can be differently calculated amounts. Another problem is deciding on the costs to use for raw materials; is it the cost of replacing the raw materials (their relevant cost) or the actual cost that was paid for them? ( Replacement cost is more logical as it is the cost of bringing in more raw materials to replace those used, however in practise actual historical cost is usually used.)
Problems arise in determining how many units of output there are in a given period. It is possible that some of the costs incurred relate to work that is still in progress and not yet completed. When completed, these units of output are included in the next period with the costs incurred in the last period. Work in progress is not a serious problem but must be taken into account to get reliable full costing information.