# DE-R-006

Source: https://xmlvalid.com/rules/DE-R-006

> If both supplier and customer are located in Germany, the element "Seller contact telephone number" (BT-42) shall be provided.

- Level: error
- Rule sets: Peppol BIS Billing 3.0 rules 3.0.21
- Context: `(/ubl-invoice:Invoice/cac:AccountingSupplierParty/cac:Party/cac:Contact | /ubl-creditnote:CreditNote/cac:AccountingSupplierParty/cac:Party/cac:Contact)[$supplierCountryIsDE and $customerCountryIsDE]`
- Test: `cbc:Telephone[boolean(normalize-space(.))]`

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