For Norwegian suppliers, a VAT number MUST be the country code prefix NO followed by a valid Norwegian organization number (nine numbers) followed by the letters MVA.
cac:AccountingSupplierParty/cac:Party[$supplierCountry = 'NO']cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/substring(cbc:CompanyID, 1, 2)='NO' and matches(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/substring(cbc:CompanyID,3), '^[0-9]{9}MVA$') and u:mod11(substring(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/cbc:CompanyID, 3, 9)) or not(cac:PartyTaxScheme[normalize-space(cac:TaxScheme/cbc:ID) = 'VAT']/substring(cbc:CompanyID, 1, 2)='NO')