# BR-DEX-06 Item standard identifier scheme must use an ISO 6523 code

Any scheme identifier on the Item standard identifier (BT-157) must be coded using one of the ISO 6523 ICD code list entries.

## Problem Description

Any scheme identifier on the Item standard identifier (BT-157) must be coded using one of the ISO 6523 ICD code list entries.

> **ERROR**: XRechnung 3.0

## Context and Significance

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

## Solution

Set the @schemeID on cac:Item/cac:StandardItemIdentification/cbc:ID to a valid ISO 6523 ICD value (for example 0160 for GTIN). If you do not need Extension item schemes such as DIGA codes, the standard XRechnung CIUS profile avoids this rule.

- validate
- convert

## Valid Examples

- <cbc:ID schemeID="0160">04012345678901</cbc:ID>

## Invalid Examples

- <cbc:ID schemeID="INTERNAL">A-100</cbc:ID> — INTERNAL is not ISO 6523

## Code Examples

### Valid XML
```
<cac:Item>
  <cac:StandardItemIdentification>
    <cbc:ID schemeID="0160">04012345678901</cbc:ID>
  </cac:StandardItemIdentification>
</cac:Item>
```

### Invalid XML
```
<cac:Item>
  <cac:StandardItemIdentification>
    <cbc:ID schemeID="INTERNAL">A-100</cbc:ID>
  </cac:StandardItemIdentification>
</cac:Item>
```

## Affected Fields

- [BT-157 Item standard identifier](/resources/xrechnung/bt-157-item-standard-identifier)

## Related Rules

- [BR-DEX-04](/resources/kosit-validator-errors/br-dex-04-party-identifier-iso-6523-scheme)
- [BR-DE-21](/resources/kosit-validator-errors/br-de-21-specification-identifier-syntax)

## 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.