In a firm with a good system of internal control, all purchases of machinery, equipment and materials must go through the Purchasing Department. The department that wishes to purchase something cannot directly order it, but instead creates a document called a requisition, which must be approved by the appropriate person (i. e. , the one with the authority to approve requisition). The approved requisition form is sent to the Purchasing Department.
The purchasing department should be familiar with various outside vendors, and it will locate the vendor who is offering the requisitioned item for the lowest possible price. It will order the goods from that vendor. It will then issue an approved purchase order and send it to the chosen vendor as the vendor’s authorization to ship the goods. The purchasing department sends a copy of the purchase order to accounts payable and to the receiving (warehouse) department that will accept the purchased goods when they arrive.
In a good system, the quantity of order goods does not appear in the receiving department’s copy, forcing that department to manually count the number of items received, to confirm independently that the number of items received equals the number ordered. When the goods are received, the receiving department creates a receiving report and delivers the goods to the requisitioning department (and it should require the requisitioning department to sign off on the report, indicating that it received the items it requisitioned).
When the vendor sends its invoice to accounts payable, that department will match that invoice to its copies of the purchase order and the receiving report, to make sure that everything on the invoice has in fact been properly ordered and received by company personnel before the invoice is authorized for payment. The purchasing department is a control on the purchase of items to be paid for by the company. It prevents company personnel in different departments from ordering items without authorization and at too high a price, and it helps to ensure that all authorized purchases are captured by the firm’s accounting system.