We have been notified that (Product) ordered on our Purchase Order No. XXXX dated MM/DD/YY is not in stock and has been back ordered. I understand that we will not receive the shipment for another _____ weeks.
Unfortunately, we have an immediate need for (Product). Please cancel the order as we will purchase it through another vendor.
Please reflect the appropriate credit of $0.00 on our next bill. When we receive the remaining order in a week, we will remit a payment for the new balance of $0.00.
Thank you for informing us about the back order in a timely manner.