A multi-level bill of materials (BOM), referred to as an indented BOM, is a bill of materials that lists the assemblies, components, and parts required to make a product in a parent-child, top-down method. It provides a display of all items that are in parent-children relationships. When an item is a sub-component, of a (parent) component, it can in-turn have its own child components, and so on. The resulting top-level BOM (item number) would include children; a mix of finished sub-assemblies, various parts and raw materials. A multi-level structure can be illustrated by a tree with several levels. In contrast, a single-level structure only consists of one level of children in components, assemblies and material.