The work order bill of material (BOM) is derived from the item’s product structure, defined in Product Structure Maintenance (or Formula Maintenance) and the quantity ordered. Inventory allocations and issues are based on the bill. MRP uses the bill of materials to calculate component demand.

When a work order is created, the product structure for the item is copied into it. This product structure with the order quantity of the work order then becomes the work order bill of material and is specific to that work order. As work progresses, required changes can be made to this copy using Work Order Bill Maintenance (16.13.1). This way, what actually happens can be compared to the standard. When many substitute items are available for assembly, this feature supports what is often called “as built” documentation.

Once created, the work order bill of material is not affected by changes to the product structure.