Message

No more than one note is allowed on document level, unless both the buyer and seller are German organizations.

Context
ubl-creditnote:CreditNote | ubl-invoice:Invoice
Test
count(cbc:Note) <= 1 or ($supplierCountryIsDE and $customerCountryIsDE)
Usage
/ ubl:Invoice / cbc:Note
/ ubl:CreditNote / cbc:Note