# BR-DE-2 Seller contact details must be provided

The seller's contact details must appear on the invoice.

## Problem Description

The seller's contact details must appear on the invoice.

> **ERROR**: XRechnung 3.0

## Context and Significance

Receivers, especially public-sector buyers, use seller contact details to clarify invoice questions, resolve mismatches, and speed up payment. Missing details often lead to manual rejection or slower processing.

## Solution

Add the seller's contact details to the invoice.

## Valid Examples

- Contact: Max Mustermann, +49 30 1234567, invoice@company.example
- Contact email provided in the seller party contact block

## Invalid Examples

- No contact element for the seller party
- Only a company name without email or phone details

## Code Examples

### Valid XML
```
<cac:AccountingSupplierParty>
  <cac:Party>
    <cac:Contact>
      <cbc:Name>Max Mustermann</cbc:Name>
      <cbc:Telephone>+49301234567</cbc:Telephone>
      <cbc:ElectronicMail>invoice@company.example</cbc:ElectronicMail>
    </cac:Contact>
  </cac:Party>
</cac:AccountingSupplierParty>
```

### Invalid XML
```
<cac:AccountingSupplierParty>
  <cac:Party>
    <!-- Missing cac:Contact -->
  </cac:Party>
</cac:AccountingSupplierParty>
```

## Technical Details

### Affected Fields
Seller Contact, Seller Contact Email, Seller Contact Telephone

## Related Rules

- [BR-DE-3](/resources/kosit-validator-errors/br-de-3-seller-city-must-be-provided)
- [BR-DE-4](/resources/kosit-validator-errors/br-de-4-seller-postal-code-must-be-provided)
- [BR-DE-5](/resources/kosit-validator-errors/br-de-5-seller-country-must-be-provided)
- [BR-DE-6](/resources/kosit-validator-errors/br-de-6-seller-name-must-be-provided)

## Validation Tools

- [Official KoSIT Validator](https://erechnungsvalidator.service-bw.de/): Validate your XRechnung files against all BR-DE rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Automatic validation error fixes when converting.

## Related Resources

- [Official Specification](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [Complete Error List](/resources/kosit-validator-errors): Overview of all German XRechnung validation rules.