Your client controls the existence and occurrence of sales by having the computer program match the information supporting sales invoices with underlying shipping documents before a sales invoice is recorded. The customer information is matched with customer information on a bill of lading, the quantities billed are matched with packing slip information, prices are matched with the sales order, and the invoice date is matched with the accounting period in which goods are shipped. If the transaction does not exactly match the underlying information it is printed on an exception report and not processed.

Required
Explain the tests of controls that need to be performed to assess control risk at a low level based on the programmed controls described above.