A Response to Invoice Received after Payment sample letter that states just the facts and requires no further responses unless an issue arises.
This is to acknowledge our receipt of your invoice #________
A check of our records indicates that payment for this invoice was made on [date] 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.