The majority of inventory accounting entries are generated when warehouses replenish and issue inventory. Warehouse managers can restock their warehouses by ordering items from an external vendor or from another warehouse. Ordering items from an external vendor is referred to as external replenishment. Ordering or purchasing items from another warehouse within your agency is referred to as internal replenishment. Inventory can be issued to customers either by filling online orders (known as usage orders in the NCAS) or by issuing the inventory directly (known as direct issue in the NCAS).