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Warning

UBL-CR-122: Leave the hash algorithm out of external attachment references

In short

Warning: worth checking.

UBL-CR-122 means your UBL invoice or credit note contains a hash algorithm (cbc:HashAlgorithmMethod) inside cac:AdditionalDocumentReference/cac:Attachment/cac:ExternalReference. Delete cbc:HashAlgorithmMethod 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:HashAlgorithmMethod, which identifies the method used to calculate a checksum. 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 hash algorithm out of external attachment references. This rule checks the XML structure, not whether anyone verifies a linked file.

How to fix it

Delete cbc:HashAlgorithmMethod 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:HashAlgorithmMethod 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 HashAlgorithmMethod

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-122 still fails, and which other rules do.

Updated 6 November 2026