Message

An Invoice shall have an Invoice type code (BT-3).

Context
/ubl:Invoice | /cn:CreditNote
Test
normalize-space(cbc:InvoiceTypeCode) != '' or normalize-space(cbc:CreditNoteTypeCode) !=''
Usage
/ ubl:Invoice / cbc:InvoiceTypeCode
/ ubl:CreditNote / cbc:CreditNoteTypeCode