Dear …

In a recent review of your account with __(company name)__, we found that you have an outstanding credit on your account. This credit balance was left on your account to be applied against future charges, however, a considerable amount of time has now elapsed and we feel that you will be better served if we issue you a refund.

Please find enclosed our refund check in the amount of __($ )__. We trust that you will find this to be acceptable and we look forward to being of service to you again soon.

Thank you for your valued business!

Yours truly,