How is independent verification carried out in a manual revenue system?

Independent verification occurs in several departments as part of the sales order processing system. The shipping department verifies that the goods released by the warehouse for shipment, as shown on the stock release document, match the packing slip. Billing compares the shipping notice with the invoice to be sure customers are billed only for goods shipped. And general ledger reconciles the journal vouchers prepared by billing, inventory control, cash receipts, and accounts receivable. This reconciliation focuses on a match between what was ordered, what was removed from the stockroom, what was shipped, what was billed, cash received, and credit to the customer account.