# BT-51 Buyer address line 2

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

## Quick answer

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

- [Validate XML](/en/xrechnung-validator?source=resource&bt=BT-51)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&bt=BT-51)

## In plain language

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.

## Where the field sits

BT-51 belongs to the Buyer part of the invoice. UBL 2.1 Syntax: Invoice › cac:AccountingCustomerParty › cac:Party › cac:PostalAddress › cbc:AdditionalStreetName. CII (UN/CEFACT) Syntax: rsm:CrossIndustryInvoice › rsm:SupplyChainTradeTransaction › ram:ApplicableHeaderTradeAgreement › ram:BuyerTradeParty › ram:PostalTradeAddress › ram:LineTwo.

## Valid Examples

- Building C

## Related Fields

- [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

## XML Implementation

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

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

## Create an XRechnung from your PDF

The converter reads the invoice and shows the fields it found before download, so you can check and correct the values. No PDF? Fill in the XRechnung directly in the form.

- [Convert invoice](/en/pdf-to-xrechnung)
- [Fill in XRechnung in the form](/en/create-xrechnung)

Trying it and buying a single conversion work without an account. Subscriptions from €10/month with annual billing (excl. taxes), or €5 per conversion (excl. taxes) without a subscription.

## Official sources and tools

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