Job costing involves the detailed accumulation of production costs attributable to specific units or groups of units. For example, the construction of a custom-designed piece of furniture would be accounted for with a job costing system. The costs of all labor worked on that specific item of furniture would be recorded on a time sheet and then compiled on a cost sheet for that job. Similarly, any wood or other parts used in the construction of the furniture would be charged to the production job linked to that piece of furniture. This information may then be used to bill the customer for work performed and materials used, or to track the extent of the company's profits on the production job associated with that specific item of furniture.
Process costing involves the accumulation of costs for lengthy production runs involving products that are indistinguishable from each other. For example, the production of 100,000 gallons of gasoline would require that all oil used in the process, as well as all labor in the refinery facility be accumulated into a cost account, and then divided by the number of units produced to arrive at the cost per unit. Costs are likely to be accumulated at the department level, and no lower within the organization.
Given these descriptions of job costing and process costing, we can arrive at the following differences between the two costing methodologies:
Uniqueness of product. Job costing is used for unique products, and process costing is used for standardized products.
Size of job. Job costing is used for very small production runs, and process costing is used for large production runs.
Record keeping. Much more record keeping is required for job costing, since time and materials must be charged to specific jobs. Process costing aggregates costs, and so requires less record keeping.
Customer billing. Job costing is more likely to be used for billings to customers, since it details the exact costs consumed by projects commissioned by customers.
In situations where a company has a mixed production system that produces in large quantities but then customizes the finished product prior to shipment, it is possible to use elements of both the job costing and process costing systems, which is known as a hybrid system.
Job costing and process costing can be used in both manual and computerized accounting environments.