# BT-10 Buyer Reference

A routing identifier assigned by the buyer for internal routing purposes

> BT-10 (Buyer reference) carries a free-text reference assigned by the buyer. For German B2G invoices under XRechnung it must hold a valid Leitweg-ID (e.g. 04011000-12345-35) per BR-DE-15. Cardinality: Mandatory in XRechnung; Optional in base EN 16931.
>
> BT-10 · EN 16931 / XRechnung 3.x

## BT Reference Card

Canonical EN 16931 / XRechnung facts for this business term — citable from this anchor.

- **BT code**: BT-10
- **Name**: Buyer Reference
- **Cardinality**: Mandatory (M) — XRechnung; Optional (O) — EN 16931
- **Business group**: BG-2 PROCESS CONTROL
- **Data type**: Text
- **Example value**: 04011000-12345-35
- **Common error**: BR-DE-15: A Buyer reference (BT-10) must be present. For German B2G receivers it must be a valid Leitweg-ID assigned by the receiving authority.
- **XRechnung note**: XRechnung promotes BT-10 from optional to mandatory (BR-DE-15) and constrains the value to a Leitweg-ID for federal/state/municipal receivers. Without a valid Leitweg-ID the invoice is rejected at the central XRechnung gateway.

## Quick answer

A routing identifier assigned by the buyer for internal routing purposes

> **Invoice basics**: Core document identifiers, dates, process identifiers, and high-level invoice context.

## In plain language

A routing identifier assigned by the buyer for internal routing purposes

A routing identifier assigned by the buyer for internal routing purposes

Essential for routing invoices to correct department in German public administration

## What you usually enter here

Text with alphanumeric characters and hyphens

Typical valid values include: 991-12345-67, 992-BW-FINANZ-2024, 993-MUC-EDU-001, 04011000-26158-01

Mandatory for all XRechnung invoices to German authorities since November 27, 2020

## What goes wrong often

Avoid values like: 12345, DE-991-12345, 991_12345_67, 991-12345-67-89-01

Relevant rule codes: BR-DE-15

## Examples in context

Essential for routing invoices to correct department in German public administration

Mandatory for all XRechnung invoices to German authorities since November 27, 2020

## Valid Examples

- 991-12345-67
- 992-BW-FINANZ-2024
- 993-MUC-EDU-001
- 04011000-26158-01

## Invalid Examples

- 12345
- DE-991-12345
- 991_12345_67
- 991-12345-67-89-01

## Related Fields

Essential for routing invoices to correct department in German public administration

- [BT-11 Project Reference](/resources/xrechnung/bt-11-project-reference)
- [BT-12 Contract reference](/resources/xrechnung/bt-12-contract-reference)
- [BT-13 Purchase Order Reference](/resources/xrechnung/bt-13-purchase-order-reference)
- [BT-19 Buyer accounting reference](/resources/xrechnung/bt-19-buyer-accounting-reference)

## XML mapping and field facts

Open the technical reference if you need XML paths, validator rule codes, legal wording, or schema-specific mapping details.

### Field ID:
BT-10

### Data Type:
text

### Cardinality:
1..1

### Requirement:
Mandatory

### Max Length:
250 characters

### Since Version:
XRechnung 1.0+

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cbc:BuyerReference
```

### CII (UN/CEFACT) Syntax
```
/CrossIndustryInvoice/SupplyChainTradeTransaction/ApplicableHeaderTradeAgreement/ram:BuyerReference
```

## Validation Rules

### BR-DE-15
Buyer Reference (BT-10) must be provided

## Why the standard cares about this field

### Business Context
Essential for routing invoices to correct department in German public administration

### Legal Requirement
Mandatory for all XRechnung invoices to German authorities since November 27, 2020

## FAQ

### Is the Buyer Reference mandatory for XRechnung?
Yes. For invoices to German public authorities, the Buyer Reference (Leitweg-ID) is mandatory.

## Official sources and tools

- [KoSIT Validator](https://erechnungsvalidator.service-bw.de/)
- [Invoice Converter](/pdf-to-xrechnung)
- [XRechnung Standard](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)