Please refer to your contract for details about pricing. The charges are billed with the same billing cycle as the transaction processing charges for e.g. if the billing cycle is set to monthly the monthly invoice will include charges for any Returns or Chargebacks.
Examples of Sender's funds being Returned:
R01: Insufficient Funds
R02: Closed Account
R08: Stop Payment
Examples of Chargebacks:
R10: Customer Advises Not Authorized
R29: Corporate Customer Advises Not Authorized