This Id is your identifier, for a given order. It has to be created by your system and then be submitted through the API inside the Payment.OrderId parameter. While not mandatory (Note, that this may be manddatory for certain 3rd party processors!), we highly recommend using it. This Id will be passed through, all the way up to the processor. It will show up inside the Saferpay Backoffice as reference number, which enables you, to search for a transaction with said OrderId. It will also show up on your reconciliation files, you get from your processor, so you are able to keep track of your transactions and it will show up on the card holders bank statement. Note, that this depends on the card holders bank. Some do not support it, even though the OrderId is set! Also, should you use PayerNote (See PayerNote), this will be used instead of the OrderId, to show up on the card holders bank statement, if supported by his bank. The OrderId however will still be used for your reconciliation files.