Greek Suppliers must provide the VAT number of the buyer, if the buyer is Greek
cac:AccountingCustomerParty[$isGreekSenderandReceiver]/cac:Party
count(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/cbc:CompanyID)=1 and substring(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/cbc:CompanyID,1,2) = 'EL' and u:TinVerification(substring(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/cbc:CompanyID,3))