A sale invoice for $ 5, 200 was computed correctly but by mistake was entered as $2, 500 to the sales journal and posted to account receivable master file the customer remitted only $ 2, 500 the amount on his monthly statement. Sales invoice number paces discounts, extentions and footings are independently checked The customers monthly statements are verified and mailed by a responsible person other than the bookkeeper who prepared them. Prelistings and predetermined totals are used to central postings. un authorized remittance deductions made by customers or other matters in dispute are investigated promptly by a person independent of the accounts receivable function