fatalEN 16931syntax binding ruleUBL
If there is a preceding invoice reference, the preceding invoice number shall be present
A preceding invoice reference group is present but carries no invoice number.
Add BT-25 — the number of the invoice being corrected or credited — in BillingReference/InvoiceDocumentReference/cbc:ID, or remove the group.
UBL — context cac:BillingReference
(cac:InvoiceDocumentReference/cbc:ID)
Nothing is stored, and the whole invoice is checked, not just this rule. A PDF only works if it is Factur-X / ZUGFeRD — a PDF with the invoice XML inside it.