All invoicing for a company is done on a computer system from a price list table incorporated into the system. Only the sales department can change the prices on the approval of the department manager. One copy of the up-to-date price list is printed monthly for verification purposes and is maintained in the sales department. The sales department keeps a list of all changes. The master price printouts are maintained for three months. The quarterly printouts, however, are maintained for one year.

Required
Identify two ways in which the auditor might gain assurance that sales transactions are properly valued.