When a sales order is entered, the product can be automatically reserved from one of your warehouses, so that quantity available for other orders are reduced by this amount. But what if some of your inventory uses either lot or serial controls? How can the order identify which lot or serial numbered item is being shipped with that order? That is done during the fulfillment process. If bar coding is not used during the pick/pack/ship process, fulfillment typically takes place as an accounting function, immediately before invoicing.