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

The customization/specification identifier should syntactically identify the XRechnung profile.

## Problem Description

The customization/specification identifier should syntactically identify the XRechnung profile.

> **WARNING**: XRechnung 3.0

## Context and Significance

This entry follows the XRechnung 3.0.2 Schematron rule semantics used by KoSIT validation.

## Solution

Use the official XRechnung BT-24 customization identifier for the target profile version.

- validate
- convert

## Valid Examples

- BT-24 Specification identifier is present and valid.

## Invalid Examples

- BT-24 Specification identifier is missing or invalid.

## Code Examples

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

### Invalid XML
```
<!-- Plain EN 16931 identifier does not identify the XRechnung profile -->
<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://erechnungsvalidator.service-bw.de/): Validate your XRechnung files against all BR-DE rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Automatic validation error fixes when converting.

## Related Resources

- [Official Specification](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [Complete Error List](/resources/kosit-validator-errors): Overview of all German XRechnung validation rules.