The sales order number set by the supplier.

recadv_Examples
 <documentReference documentType="SupplierOrder" id="24123456" date="2020-10-01">
recadv_XPATH

/b24Message/receivingAdvice/documentReference[@documentType="SupplierOrder"]/@id

recadv_Required
Yes
recadv_Sort
8
Subscribe to (Header) : Supplier order number