Traceability of Overhead Costs
A costing system uses three methods to assign costs to individual products: direct tracing, driver tracing, and allocation. Of the three methods, direct tracing is the most accurate and thus, is preferred over the other two methods. In a departmental structure, many different products may be subjected to a process located in a single department (for example, grinding). After completion of the process, the products are then transferred to other processes located in different departments (for example, assembly, painting, and so on). Because more than one product is processed in a department, the costs of that department are shared by all products passing through it and, therefore, must be assigned to products using activity drivers (and occasionally allocation). In a JIT environment many overhead costs assigned to products using either tracing or allocation are now directly traceable to products. Cellular manufacturing, multiskilled labor, and decentralized service activities are the major features of JIT responsible for this change in traceability Exhibit 14-5 compares the traceability of some selected costs in a traditional manufacturing environment with their traceability in the JIT environment (assuming single-product cells). Comparisons are based on the three cost assignment methods