What it means
When the seller is Greek and the seller's address country code (BT-40) is GR, the UBL invoice or credit note must contain exactly one cac:AdditionalDocumentReference whose cbc:DocumentDescription equals ##M.AR.K##. This test counts references. It does not check whether their cbc:ID values are present or valid.
Why it matters
A single labelled reference gives software one place to find the document's MARK number. This check does not establish whether the recipient will accept the document.
How to fix it
Find the additional document references labelled ##M.AR.K##. Add one if none exists, or remove duplicate matching references if there are several. Put the MARK issued for this document in that reference's cbc:ID. Leave unrelated references in place and check the corrected file again.
Once the file is corrected, check it again for free: Validate a Peppol BIS invoice
Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice
The rule as published
Read the rule on the publisher's site
Where this rule applies
| Rule set | Version |
|---|---|
| Peppol BIS Billing 3.0 (invoice) | 2026.5 |
| Peppol BIS Billing 3.0 (credit note) | 2026.5 |
Check your file
Drop your e-invoice to see whether GR-R-004-1 still fails, and which other rules do.