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 should contain exactly one cac:AdditionalDocumentReference whose cbc:DocumentDescription equals ##INVOICE|URL##. Zero or more than one triggers this warning. The test counts references and does not inspect the web address.
Why it matters
The Greek rules recommend one reference for the invoice web address. More than one matching reference also fails GR-R-008-2, which is a fatal rule, so duplicate references are not merely a warning.
How to fix it
If the reference is missing, add one cac:AdditionalDocumentReference with cbc:DocumentDescription set to ##INVOICE|URL##. Put the invoice web address in cac:Attachment/cac:ExternalReference/cbc:URI inside it. If several matching references exist, keep one and remove the extras. If you omit the reference, this warning remains. Check the corrected file and review its other findings too.
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-S-008-1 still fails, and which other rules do.