# BR-DE-21 Specification identifier should match the XRechnung syntax

Under the XRechnung standard specification, the specification identifier (BT-24 / CustomizationID) declares the exact profile and extension version to which the electronic invoice conforms. For XRechnung 3.0.x, the specification identifier must match the official Uniform Resource Name (URN): "urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0". Validation engines and recipient gateways (such as KoSIT validator and Peppol access points) use this identifier to select the applicable Schematron rulepack and verify profile compliance.

## Problem Description

> **WARNING**: German XRechnung rule (KoSIT, BR-DE) · XRechnung 3.0

## Context and Significance

An incorrect or plain EN 16931 CustomizationID prevents the KoSIT validator from recognizing the XRechnung extension, causing national rule validation to be bypassed or flagged as a profile mismatch.

## Solution

In your XML generator or e-invoicing export module, set BT-24 to the official XRechnung 3.0 CustomizationID string: urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0. In UBL 2.1 syntax, populate <cbc:CustomizationID> directly under <Invoice> or <CreditNote>. In UN/CEFACT CII syntax, populate <ram:GuidelineSpecifiedDocumentContextParameter><ram:ID> inside <rsm:CrossIndustryInvoice><rsm:ExchangedDocumentContext>.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-DE-21)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-DE-21)

## Valid Examples

- BT-24 = "urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0"
- BT-24 = "urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0#conformant#urn:xeinkauf.de:kosit:extension:xrechnung_3.0" (XRechnung extension)

## Invalid Examples

- BT-24 = "urn:cen.eu:en16931:2017" (Base EN 16931 identifier without XRechnung extension URN)
- BT-24 = "XRechnung_3.0" (Informal text string instead of standardized URN syntax)
- BT-24 = "urn:cen.eu:en16931:2017#compliant#urn:xoev-de:kosit:standard:xrechnung_2.3" (Legacy XRechnung 2.x identifier; not valid for XRechnung 3.0)
- BT-24 = "urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0" (Peppol BIS Billing 3.0 is a different CIUS, not an XRechnung identifier)

## Code Examples

### Valid XML
```
<cbc:CustomizationID>urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0</cbc:CustomizationID>
```

### Invalid XML
```
<cbc:CustomizationID>urn:cen.eu:en16931:2017</cbc:CustomizationID>
```

## Affected Fields

- [BT-24 Specification identifier](/resources/xrechnung/bt-24-specification-identifier)

## Related Rules

- [BR-01](/resources/kosit-validator-errors/br-01-specification-identifier-required)

## Validation Tools

- [Official KoSIT Validator](https://github.com/itplr-kosit/validator): Run the official KoSIT validator with the XRechnung configuration to check EN 16931 and XRechnung rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Find validation errors during conversion and review each correction.

## Related Resources

- [Official Specification](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [All validation errors](/resources/kosit-validator-errors): Overview of the EN 16931, XRechnung and Peppol validation rules explained here.