This is very important for Job Order* and Process Costing. It is tough to allocate the many miscellaneous costs which are attributed to the manufactur of goods.
Costs which can not be directly traceable
These include a combination of both fixed and variable costs:
Indirect Labor
Factory Insurance
Factory Rent
For simplicity of paperwork, an estimated amount of overhead (OH) may be calculated and charged to jobs or products:
Estimated total MFG OH / Estimated total units MFG = Predetermined OH Rate
Once this rate is known, it may be allocated:
Predetermined OH rate * Actual Labour Hours = Applied OH