A bill of materials (BOM) is a formal and complete hierarchal documentation of the specific items that need to be included in a finished product. This list can include specific components, assemblies, and subassemblies. Bills of materials can be drafted at the onset of a project as part of the estimating and budgeting process, and can also be used in the determination of scheduling. Bills of materials are used in a number of different industries. One rather simplistic example of a bill of material would be the following. In a plant devoted to the manufacture and packaging of a billards set for retail sale, the bill of materials would include all components required to be in the final box for sale (billiards cues, billards balls, chalk, billards table), all of the assemblies required (assembling the pool cues, assembling the billiards table), and all subassemblies (attaching the felt surface to the billards table, etc.). The bill of materials is typically one of the first items drafted upon project inception.
This term is defined in the 3rd edition of the PMBOK but not in the 4th.