If both supplier and customer are located in Germany, and if "Payment means type code" (BT-81) contains a code for payment card (48, 54, 55), "PAYMENT CARD INFORMATION" (BG-18) shall be provided.
(/ubl-invoice:Invoice/cac:PaymentMeans[normalize-space(cbc:PaymentMeansCode) = ('48','54','55')] |/ubl-creditnote:CreditNote/cac:PaymentMeans[normalize-space(cbc:PaymentMeansCode) = ('48','54','55')])[$supplierCountryIsDE and $customerCountryIsDE]cac:CardAccount