Request for Refund of Duplicate Payment

Dear
On (date) , this office mailed to you a check

in the amount of $ per your (date) invoice.
After reviewing your file, I realized that this account

had been paid in full on (date) I am enclosing

a photocopy of our cancelled check # in the amount

of $
I would appreciate it if you would reimburse this office

for the duplicate payment. I apologize for any

inconvenience this error has caused.
Thank you for your prompt attention to this matter.