Contains vendor-specific extensions
The invoice contains an extension block (UBLExtensions) with vendor-specific extra data. The EN 16931 standard does not provide for such extensions.
What to do now
Who has to fix this?
Only the issuer or the vendor of their invoicing software can fix this. As a recipient you can usually accept an invoice with such warnings; portals of public-sector buyers, however, reject some of them.
Where this rule comes from
The file formats UBL and CII can express far more than the European standard EN 16931 provides for an invoice. Around 1,300 syntax rules (UBL-CR, UBL-SR, UBL-DT, CII-SR, CII-DT) define which of these additional fields should not be used and which details may appear only once. Most of these rules are warnings: the invoice remains complete in content but contains details that the recipient will not read automatically.
- Rule ID
- UBL-CR-001
- Rule set
- Syntax rules (UBL and CII)
- Checked for
- XRechnung, ZUGFeRD, Factur-X, Peppol BIS and other EN 16931 formats
- Consequence of a violation
- The invoice is considered non-compliant with the standard and is automatically rejected by many recipients.
Does UBL-CR-001 occur in your invoice?
Upload the XRechnung or the ZUGFeRD/Factur-X PDF – the validator shows every violation with the same explanation as here. Free, no login, nothing stored.
Validate your invoice nowGeneral information, not tax or legal advice. As of October 2026. Validation rules: CEN/TC 434 (EN 16931, EUPL 1.2), KoSIT (XRechnung, Apache 2.0), FNFE-MPE/FeRD (Factur-X/ZUGFeRD, Apache 2.0), OpenPeppol AISBL (Peppol BIS), ANAF (CIUS-RO). Explanations: Billvox. Licence notices