Examine any correspondence from customers in which they complain about incorrect pricing and then compare the sales invoice to the official price list, to see if there really was a mistake.

Have the clerk walk you through the process of creating a sales invoice and checking that the prices on the invoice are compared to the prices on the list.

Compare the amount on the sales invoice to the amount recorded in the sales journal to see that they are the same.

Take a sample of sales invoices and check that the prices are the same as those on the company price list.