APOLOGY FOR INCORRECT PAYMENT: UNDERPAYMENT
Allow me to apologize for the incorrect payment we made to you regarding your invoice #[INVOICE NUMBER]. Our check #[CHECK NUMBER] for $[AMOUNT] is short of the total amount due, $[ AMOUNT].
Enclosed, please find our check #[CHECK NUMBER] for $[AMOUNT], representing the difference between $[AMOUNT] and [AMOUNT].
Please accept my apologies and assurance that this will not occur again.