# BR-DE-15 Buyer reference must be provided

Under § 4 Abs. 1 Nr. 1 of the German E-Rechnungsverordnung (E-Rech-V) and the core XRechnung standard, every electronic invoice submitted to a German public sector contracting entity MUST include a valid buyer reference (BT-10). For public sector buyers in Germany (federal ministries, federal states/Bundesländer, and municipalities), the buyer reference takes the form of a standardized routing code known as the Leitweg-ID (e.g. "04011000-12345-34" or "991-12345-67"). Public invoice receipt platforms, such as OZG-RE (direct federal administration, more than 170 indirect federal bodies and several Länder) and other state or municipal portals, use the Leitweg-ID to automatically route incoming invoices to the specific approval workflow, cost center, and budget officer.

## Problem Description

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

## Context and Significance

Without a valid BT-10 Leitweg-ID, public invoice receipt platforms such as OZG-RE (direct federal administration, more than 170 indirect federal bodies and several Länder) and other state or municipal portals reject the invoice immediately at the portal boundary, before any manual review can take place.

## Solution

Obtain the official Leitweg-ID or buyer reference code from your client’s procurement order, tender documentation, or contract. In your ERP software (such as SAP SD, DATEV, or Dynamics 365), maintain this code in the customer order reference or buyer reference field. In UBL 2.1 syntax, populate <cbc:BuyerReference> directly under the root <Invoice> element. In UN/CEFACT CII syntax, populate <ram:BuyerReference> under <rsm:CrossIndustryInvoice><rsm:SupplyChainTradeTransaction><ram:ApplicableHeaderTradeAgreement>.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-DE-15)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-DE-15)

## Valid Examples

- BT-10 = "04011000-12345-34" (Valid German state authority Leitweg-ID with 2-digit check digit)
- BT-10 = "991-12345-67" (Valid federal agency Leitweg-ID)

## Invalid Examples

- Invoice header completely omits the cbc:BuyerReference / ram:BuyerReference element
- Buyer reference left as empty string or populated with placeholder text when billing public authorities

## Code Examples

### Valid XML
```
<cbc:BuyerReference>04011000-12345-34</cbc:BuyerReference>
```

### Invalid XML
```
<cbc:ID>RE-2026-001</cbc:ID>
<cbc:IssueDate>2026-01-15</cbc:IssueDate>
```

## Affected Fields

- [BT-10 Buyer reference](/resources/xrechnung/bt-10-buyer-reference-leitweg-id)

## 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.