A bill of material coding and structuring technique used primarily for transient (non-stocked) sub-assemblies. For the transient sub-assembly item, lead time is set to zero and the order quantity to lot-for-lot. This permits MRP logic to drive requirements straight through the phantom item to its components, but retains its ability to net against any occasional inventories of the sub-assembly. This technique also facilitates the use of common bills of material for Engineering and Manufacturing.