The reason is that the internal warehouse management of the enterprise takes the outbound order as the picking voucher. According to the information of warehouse documents, warehouse documents confirm the quantity of purchased goods, and at the same time monitor the buyers and suppliers, so they lack the control of physical goods, and cannot prevent the buyers and suppliers from colluding with fraud, falsely reporting the purchase quantity and the risk of physical goods shortage, which is an important certificate for internal control of enterprises. In fact, the receipt and delivery documents are the vouchers for goods transfer between merchants. Only when the warehouse management in the enterprise takes the outbound order as the delivery voucher, the consignee (the consignee) must sign and affix the official seal (receipt seal) at the same time, which can be regarded as a valid voucher and make the accounting details clear.