Process costing is used when there is mass production of similar products, where the costs associated with individual units of output cannot be differentiated from each other. In other words, the cost of each product produced is assumed to be the same as the cost of every other product. Under this concept, costs are accumulated over a fixed period of time, summarized, and then allocated to all of the units produced during that period of time on a consistent basis. When products are instead being manufactured on an individual basis, job costing is used to accumulate costs and assign the costs to products. When a production process contains some mass manufacturing and some customized elements, then a hybrid costing system is used.
