Use to store additional information associated with the payment. You can add parameters udf1 and udf2 to pass your internal values such as transactionId, chargeId, orderId, bundleId, or affiliateId. Any values passed will be available in the Merchant Portal

Custom fees of the merchant. If omitted, the standard fees of the merchant are applied.
If passed, they are used instead of the standard fees.
If none of the passed fees matches the customer country and the payment method, no fee is added.
VAT is charged on the amount of the Platform Fee only. For other fees it is charged on the price together with the fees