Notice to customer: require pre-payment on next order

We thank you for your payment of $[AMOUNT, ex. 5,000.23] for [PRODUCT(S) / SERVICE(S), ex. your order of five Magnaflux compressors]. As you know, we greatly appreciate your business. Although your payment was [X] days overdue, we understand your position; cash flow is indeed tight these days for all firms. We wish to offer you the best service possible. For this reason, we will require a pre-payment on future order{s}. I'm certain you will find this reasonable, as our suppliers and creditors also hold us to strict terms. [MENTION LENGTH OF REQUIRED PRE-PAYMENT OR REVIEW PROCESS, ex. Since you have been a good customer, we will be glad to review your account in the next six months to offer you better credit terms.] Sincerely,