Response to Invoice Received After Payment
This is to acknowledge our receipt of your invoice # [#]. A check of our records indicates that payment for this invoice was made on [12-10-2012] with our check #[#] payable to you in the amount of $.
Please review your records and bank deposits to be sure that you have not received our payment. If you are still unable to find a record of payment, let me know, and I will request a photocopy of our check, and forward it to your office. This normally takes about 30 days.
If I do not hear from you, I will assume that you have found our payment and have appropriately credited our account