# BR-63 Buyer electronic address must have a scheme identifier

The Buyer electronic address (BT-49) shall have a Scheme identifier that names the electronic address scheme.

## Problem Description

The Buyer electronic address (BT-49) shall have a Scheme identifier that names the electronic address scheme.

> **ERROR**: XRechnung 3.0

## Context and Significance

This rule comes from the EN16931 core semantic model enforced by the KoSIT XRechnung 3.0.2 Schematron, ensuring invoices carry the mandatory data needed for automated processing.

## Solution

Set the schemeID attribute on cbc:EndpointID for the buyer using an EAS code that matches how the buyer receives invoices.

- validate
- convert

## Valid Examples

- BT-49 = 991-1234567-89 with schemeID="9958" (Leitweg-ID)

## Invalid Examples

- BT-49 EndpointID present but with no schemeID attribute

## Code Examples

### Valid XML
```
<cac:AccountingCustomerParty>
  <cac:Party>
    <cbc:EndpointID schemeID="9958">991-1234567-89</cbc:EndpointID>
  </cac:Party>
</cac:AccountingCustomerParty>
```

### Invalid XML
```
<cac:AccountingCustomerParty>
  <cac:Party>
    <cbc:EndpointID>991-1234567-89</cbc:EndpointID>
  </cac:Party>
</cac:AccountingCustomerParty>
```

## Affected Fields

- [BT-49 Buyer electronic address](/resources/xrechnung/bt-49-buyer-electronic-address)

## Related Rules

- [BR-62](/resources/kosit-validator-errors/br-62-seller-electronic-address-scheme-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.