# BR-18 Seller tax representative name is required when the party is present

The Seller tax representative name (BT-62) shall be provided when the Seller (BG-4) has a Seller tax representative party (BG-11).

## Problem Description

> **ERROR**: EN 16931 core business rule (CEN)

## Context and Significance

This is a conditional EN 16931 core rule. A tax representative meets VAT obligations on behalf of a seller that is not established in the member state, so the representative must be named on the invoice. The error often appears when only the representative’s VAT identifier is copied into the export. In UBL the name is cac:TaxRepresentativeParty/cac:PartyName/cbc:Name; in CII, BT-62 is ram:SellerTaxRepresentativeTradeParty/ram:Name.

## Solution

When a cac:TaxRepresentativeParty group is present, add cac:TaxRepresentativeParty/cac:PartyName/cbc:Name with its name.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-18)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-18)

## Valid Examples

- cac:TaxRepresentativeParty present with BT-62 = VAT Rep Services Ltd

## Invalid Examples

- cac:TaxRepresentativeParty is present but has no cac:PartyName/cbc:Name

## Code Examples

### Valid XML
```
<cac:TaxRepresentativeParty>
  <cac:PartyName>
    <cbc:Name>VAT Rep Services Ltd</cbc:Name>
  </cac:PartyName>
</cac:TaxRepresentativeParty>
```

### Invalid XML
```
<cac:TaxRepresentativeParty>
  <cac:PostalAddress>
    <cac:Country>
      <cbc:IdentificationCode>DE</cbc:IdentificationCode>
    </cac:Country>
  </cac:PostalAddress>
</cac:TaxRepresentativeParty>
```

## Affected Fields

- [BT-62 Seller tax representative name](/resources/xrechnung/bt-62-seller-tax-representative-name)
- [BG-11 Seller tax representative party](/resources/xrechnung/bt-62-seller-tax-representative-name)

## Related Rules

- [BR-19](/resources/kosit-validator-errors/br-19-tax-representative-address-required)
- [BR-20](/resources/kosit-validator-errors/br-20-tax-representative-country-code-required)

## 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://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/)
- [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.