Job costing is accounting which tracks the costs and revenues by "job" and enables standardized reporting of profitability by job. For an accounting system to support job costing, it must allow job numbers to be assigned to individual items of expenses and revenues. A job can be defined to be a specific project done for one customer, or a single unit of product manufactured, or a batch of units of the same type that are produced together.

To apply job costing in a manufacturing setting involves tracking which "job" uses various types of direct expenses such as direct labour and direct materials, and then allocating overhead costs (indirect labor, warranty costs, quality control and other overhead costs) to the jobs. A job profitability report is like an overall profit & loss statement for the firm, but is specific to each job number.

Job costing may assess all costs involved in a construction "job" or in the manufacturing of goods done in discrete batches. These costs are recorded in ledger accounts throughout the life of the job or batch and are then summarized in the final trial balance before the preparing of the job cost or batch manufacturing statement.