# BT-51 Buyer address line 2

Additional address information for the buyer, such as building, floor, or department.

## Quick answer

Additional address information for the buyer, such as building, floor, or department.

> **Buyer details**: Who receives the invoice and which buyer records or routing data must match.

## In plain language

Additional address information for the buyer, such as building, floor, or department.

Additional address information for the buyer, such as building, floor, or department.

Use this when one buyer address line is not enough to route the invoice correctly.

## What you usually enter here

Additional address details

Typical valid values include: Building C

Optional according to EN 16931-1.

## What goes wrong often

Avoid values like:

## Examples in context

Use this when one buyer address line is not enough to route the invoice correctly.

Optional according to EN 16931-1.

## Valid Examples

- Building C

## Related Fields

Use this when one buyer address line is not enough to route the invoice correctly.

- [BT-50 Buyer Address Line 1](/resources/xrechnung/bt-50-buyer-address-line-1)
- [BT-52 Buyer City](/resources/xrechnung/bt-52-buyer-city)

## 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-51

### Data Type:
text

### Cardinality:
0..1

### Requirement:
Optional

### Max Length:
100 characters

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:AccountingCustomerParty/cac:Party/cac:PostalAddress/cbc:AdditionalStreetName
```

### CII (UN/CEFACT) Syntax
```
/CrossIndustryInvoice/SupplyChainTradeTransaction/ApplicableHeaderTradeAgreement/ram:BuyerTradeParty/ram:PostalTradeAddress/ram:LineTwo
```

## Why the standard cares about this field

### Business Context
Use this when one buyer address line is not enough to route the invoice correctly.

### Legal Requirement
Optional according to EN 16931-1.

## 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)