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Warning

UBL-CR-121: Leave the file hash out of external attachment references

In short

Warning: worth checking.

UBL-CR-121 means your UBL invoice or credit note contains a document hash (cbc:DocumentHash) inside cac:AdditionalDocumentReference/cac:Attachment/cac:ExternalReference. Delete cbc:DocumentHash from that external reference and check the file again.

On this page

What it means

This rule checks that no cac:AdditionalDocumentReference/cac:Attachment/cac:ExternalReference in a UBL invoice or credit note contains cbc:DocumentHash, a checksum value for the referenced file. For a supporting document (BG-24), the external link (BT-124) is held in cbc:URI in the same external reference. The check applies whether or not cbc:URI is present.

Why it matters

EN 16931 recommends leaving the document hash out of external attachment references. This rule checks the XML structure, not whether a linked file has changed.

How to fix it

Delete cbc:DocumentHash from cac:AdditionalDocumentReference/cac:Attachment/cac:ExternalReference and leave any cbc:URI there unchanged. If you use invoicing software, ask its supplier to stop exporting cbc:DocumentHash at that location. Recheck the corrected file.

Once the file is corrected, check it again for free: Validate an invoice against EN 16931

Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice

The rule as published

A UBL invoice should not include the AdditionalDocumentReference Attachment External DocumentHash

Where this rule applies

Rule set Version
EN 16931 (UBL) 1.3.17
EN 16931 (UBL credit note) 1.3.17
XRechnung 3.0 (UBL) 3.0.2
XRechnung 3.0 (UBL credit note) 3.0.2
Peppol BIS Billing 3.0 (invoice) 2026.5
Peppol BIS Billing 3.0 (credit note) 2026.5
SI-UBL 2.0 / NLCIUS (invoice) 2.0.3.13
SI-UBL 2.0 / NLCIUS (credit note) 2.0.3.13
France CTC (UBL invoice) 1.4.0-04
France CTC (UBL credit note) 1.4.0-04
CIUS-RO UBL Invoice 1.0.9 1.0.9
CIUS-RO UBL Credit Note 1.0.9 1.0.9
Rule text from phive-rules 4.6.4.

Check your file

Drop your e-invoice to see whether UBL-CR-121 still fails, and which other rules do.

Updated 6 November 2026