Message

A buyer reference or purchase order reference MUST be provided.

Context
ubl-creditnote:CreditNote | ubl-invoice:Invoice
Test
cbc:BuyerReference or cac:OrderReference/cbc:ID
Usage
/ ubl:Invoice / cbc:BuyerReference
/ ubl:Invoice / cac:OrderReference / cbc:ID
/ ubl:CreditNote / cbc:BuyerReference
/ ubl:CreditNote / cac:OrderReference / cbc:ID