Hi Stefan,
If the payment process is done via webshop, I would propose to create the sales order or customer invoice with payment method "External payment". After you received the list of payments from the payment provider and uploading the bank statement into ByD the open item is cleared automatically.
A second alternative would be to get the transaction ID from the payment provider and to create the ByD sales order and customer invoice with payment type "External payment" and transaction ID. As result the ByD payment order contains the transaction ID and the open item is cleared based on the transaction ID (the payment monitor shows the external payment in status "in transit"). However, for automatic clearing the payment file of the payment provider has to be uploaded as standard format for bank statements (MT940). It might be that the payment file has to be converted before it can be uploaded to ByD.
Best regards,
Knut