Definition (according to business dictionary)
An order-specific costing technique, used in situations where each job is different and is performed to the customer's specifications. Job costing involves keeping an account of direct and indirect costs. Since both types of costs are usually closely related (a job requiring high input of labor and material is likely to consume more power, machine time, supervision time, inspection time, etc.) indirect costs may be applied as an estimated fraction of direct costs. Job costing methods are similar to contract costing and batch costing methods, and are used in construction, motion picture, and shipping industries, in fabrication, repair, and maintenance works, and in services such as auditing.
Read more: http://www.businessdictionary.com/definition/job-costing.html#ixzz26FvrOEVg (according to wikipedia)
Job Costing involves the calculation of costs involved in a construction "job" or 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.  Using job costing
In a job costing system, costs may be accumulated either by job or by batch. For a typical job, direct material, labor, subcontract costs, equipment, and other direct costs are tracked at their actual values. These are accrued until the job or batch is completed. Overhead or "burden" may be applied either by using a rate based on direct labor hours or by using some other Activity Based Costing (ABC) cost driver. In either case, once overhead/burden is added, the total cost for the job can be determined. If the accountant is using a general ledger accounting system, which lacks true job costing functionality, the costs must be manually transferred out of Work in Process to Finished Goods (Cost of Goods Sold for service industries). Of course, in the days of computerized job costing software, journaling costs manually is an obsolete process. Such hand-journaling is mandatory for companies that continue to use general accounting software to do job costing. Enlightened accountants are moving forward and using job costing software, thereby improving cost control, reducing risk, and increasing the chance of profitability. Using cost codes in budgeting
In a true job cost accounting system, a Budget is set up in advance of the job. As actual costs are accrued, they are compared to budgeted costs, to determine variances for each phase of each job. Cost Codes are used for each phase, allowing "mini-budgets" to be generated and tracked. In the construction industry, the Construction Specifications Institute (CSI) has established an industry standard Cost Coding system.job costing system consists of various cost driver that drives job cost, moreover it  Example
These examples will assume that overhead is allocated on the basis of Direct Labor Hours. Direct Material is abbreviated DM, Direct Labor as DL, and Overhead as OH. XYZ corporation manufactures airplanes. 1 order was completed (#110), 2 received further work (#111, 112), and 1 new order was received (#113). Overhead is allocated at a rate of $100/DL Hour. All employees earn $20/hour. Beginning Work In Process Balances are as follows: #110, $25,000; #111, $10,000; #112, $12,000; #113 $0 (New Order). Below are the amounts of DM and DL used. •#110 $2,000 DM, 25 DL hours. Therefore, $5,000 in new cost is added ($2,000 DM, $500 DL, $2,500 OH). The job had a total cost of $30,000. this amount is transferred out of Work in Process to Finished Goods or Cost of Goods Sold. •#111 $3,000 DM, 30 DL hours. Therefore, $6,600 in new cost is added ($3,000 DM, $600 DL, $3,000 OH). The job has a new total cost of $16,600. This amount remains in Work in Process until completion. •#112 $5,000 DM, 100 DL hours. Therefore, $17,000 in new cost is added ($5,000 DM,...