CBP cannot reverse the transmission. If the payment exceeds the amount due, CBP applies the payment and refunds the excess to your company. Refunds are made through the existing Treasury check disbursement process, not through ACH. If payment is less than the amount due, you will be notified via fax of the amount due and will need to send additional balance through the ACH system. Once additional amount due is received then your statement can be paid. CBP can not partially pay statements. Statements will be credited as of the collection date that the complete payment is received.