# BR-DEX-04 Party identifier scheme must use an ISO 6523 code

Any scheme identifier on a party identifier (Seller BT-29, Buyer BT-46, Payee BT-60) must be coded using one of the ISO 6523 ICD code list entries.

## Problem Description

> **ERROR**: XRechnung extension rule (KoSIT, BR-DEX) · XRechnung 3.0

## Context and Significance

This XRechnung Extension rule fires only in the Extension scenario, which relaxes the core severity to permit additional ISO 6523 scheme codes (such as DIGA identifiers) for party identifiers.

## Solution

Set the @schemeID on cac:PartyIdentification/cbc:ID to a valid ISO 6523 ICD value (for example 0088 for GLN). If you do not need Extension identifiers, the standard XRechnung CIUS profile avoids this rule.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-DEX-04)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-DEX-04)

## Valid Examples

- <cbc:ID schemeID="0088">4012345000009</cbc:ID>

## Invalid Examples

- <cbc:ID schemeID="XYZ">4012345000009</cbc:ID> — XYZ is not an ISO 6523 code

## Code Examples

### Valid XML
```
<cac:PartyIdentification>
  <cbc:ID schemeID="0088">4012345000009</cbc:ID>
</cac:PartyIdentification>
```

### Invalid XML
```
<cac:PartyIdentification>
  <cbc:ID schemeID="XYZ">4012345000009</cbc:ID>
</cac:PartyIdentification>
```

## Affected Fields

- [BT-29 Seller identifier](/resources/xrechnung/bt-29-seller-identifier)
- [BT-46 Buyer identifier](/resources/xrechnung/bt-46-buyer-identifier)
- [BT-60 Payee identifier](/resources/xrechnung/bt-60-payee-identifier)

## Related Rules

- [BR-DEX-05](/resources/kosit-validator-errors/br-dex-05-legal-registration-iso-6523-scheme)
- [BR-DE-21](/resources/kosit-validator-errors/br-de-21-specification-identifier-syntax)

## 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.