APOLOGY FOR INCORRECT PAYMENT: OVERPAYMENT
A check of our records has revealed that we have made an incorrect payment to you in settlement of your invoice #[INVOICE NUMBER]. Our check #[CHECK NUMBER] for $[AMOUNT] is $[AMOUNT] in overpayment of the total amount due, $[AMOUNT].
[MENTION HOW YOU REQUEST THE OVERPAYMENT TO BE HANDLED, ex. As the overpayment is not insignificant, I would greatly appreciate the difference of $1,000 to be sent to us.] I thank you for your consideration and look forward to continued business together.