What it means
Every invoice must contain a specification identifier (BT-24). It is a technical code, such as urn:cen.eu:en16931:2017, that tells the recipient which standard and which national or network rules the file follows.
Why it matters
The recipient's system reads this code first to decide which rules to check the invoice against. Without it the file cannot be processed at all and is rejected.
How to fix it
You do not type this code yourself. Choose the right output format in your invoicing software (for example XRechnung, ZUGFeRD, Factur-X or Peppol BIS) and export again. If you build the XML yourself, add cbc:CustomizationID in UBL or ram:GuidelineSpecifiedDocumentContextParameter/ram:ID in CII with the identifier of the standard you follow.
The rule as published
An Invoice shall have a Specification identifier (BT-24). Business terms: BT-24
Where this rule applies
| Rule set | Version |
|---|---|
| EN 16931 (UBL) | 1.3.17 |
| EN 16931 (UBL credit note) | 1.3.17 |
| EN 16931 (CII) | 1.3.17 |
| XRechnung 3.0 (UBL) | 3.0.2 |
| XRechnung 3.0 (UBL credit note) | 3.0.2 |
| XRechnung 3.0 (CII) | 3.0.2 |
| Peppol BIS Billing 3.0 (invoice) | 2026.5 |
| Peppol BIS Billing 3.0 (credit note) | 2026.5 |
| Factur-X 1.09 MINIMUM | 1.0.9-2 |
| Factur-X 1.09 BASIC WL | 1.0.9-2 |
| Factur-X 1.09 BASIC | 1.0.9-2 |
| Factur-X 1.09 EN 16931 | 1.0.9-2 |
| Factur-X 1.09 EXTENDED | 1.0.9-2 |
| ZUGFeRD 2.5 MINIMUM | 2.5.2 |
| ZUGFeRD 2.5 BASIC WL | 2.5.2 |
| ZUGFeRD 2.5 BASIC | 2.5.2 |
| ZUGFeRD 2.5 EN 16931 | 2.5.2 |
| ZUGFeRD 2.5 EXTENDED | 2.5.2 |
| SI-UBL 2.0 / NLCIUS (invoice) | 2.0.3.13 |
| SI-UBL 2.0 / NLCIUS (credit note) | 2.0.3.13 |
| NLCIUS (CII) | 1.0.3.13 |
| France CTC (UBL invoice) | 1.4.0-04 |
| France CTC (UBL credit note) | 1.4.0-04 |
| France CTC (CII) | 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 |
Check your file
Drop your e-invoice to see whether BR-01 still fails, and which other rules do.