Can you explain the control procedures over recording purchases?

Timely recording and independent review of transaction: There are two ways to record purchases: 1- On the basis of receipt of goods or services. 2- recording is deferred until the vendor's invoice is received. Accounts payable staff typically has responsibility for verifying the appropriateness of acquisition. This is done by comparing the details on the purchase order, the receiving report, and the vendor's invoice to determine that the description, prices, quantities, terms, and the vendor's invoice are correct. An important control in the audit of acquisition is that the personnel who record acquisition don't have access to cash, marketable securities and other assets. Adequate documents and records, proper procedures for record keeping and independent checks on performance are also necessary controls in the accounts payable functions.