Take example of printing press, motor workshop and all they will be undertaking work on the basis of customers order only .it means they won’t sell one product to all they will be building or developing what customers says .in order to bill customers. cost of each job have to be ascertained separately so when you ascertain cost of each job separately. we call it as job costing. This costing Method can be used for non standard products non repetitive products which are produced as per customer specifications against specific orders .Here each and every job are different from each other and they also independent of each other. It means each job is unique so cost of each job have to be ascertained separately.