DE-R-003: If both supplier and customer are located in Germany, the element "Seller city" (BT-37)…

For UBL invoices and credit notes, when both the supplier's and the customer's country identification code equal 'DE' (case-insensitive, ignoring surrounding whitespace), the supplier's postal address must contain a cbc:CityName element whose normalized text is not empty. A document fails this fatal rule if either the supplier or customer country is not 'DE' the rule does not apply, but if both are 'DE' and the supplier's cac:PostalAddress has no cbc:CityName or the element is missing or contains only whitespace, validation fails.

Ensure that within cac:AccountingSupplierParty/cac:Party/cac:PostalAddress there is a cbc:CityName element containing the supplier's city (for example <cbc:CityName>Berlin</cbc:CityName>). The element must be present and have non-whitespace content. If the supplier and customer country codes are not both DE, this rule does not require a city. Check the producer of the invoice to populate the supplier city when both parties are in Germany.