Bill of materials (BOM) is the term used to describe the "parts list" of components needed to complete a saleable end-item. BOMs are hierarchical in nature with the top level representing the sub-assembly or end-item. For example the end-item BOM for a Personal computer would list the computer, its major sub-assemblies (board, chassis, modem, keyboard, display, etc.) as well as additional materials needed for a complete saleable product -- shipping box, user manual, packaging, packaging labels, etc. The BOMs that describe the sub-assemblies are referred to as Modular BOMs. An example of this is the NAAMS BOM that is used in the automative industry to list all the components in an assembly line. The structure of the NAAMS BOM is System, Line, Tool, Unit and Detail.
A bill of material can define products as they are designed (Engineering Bill of Material), as they are ordered (Sales BOM), as they are built (Manufacturing bill of material), or as they are maintained (Service BOM). The different types of bills of materials dependent upon the business need and use for which they are intended. A bill of material can be displayed in following formats:
- the single-level bill of material,
- indented bill of material,
- modular (planning) bill of material
In process industries the bill of material is also known as the formula, recipe, or ingredients list
