In an Invoice line (BG-25) where the Invoiced item VAT category code (BT-151) is "Standard rated" the Invoiced item VAT rate (BT-152) shall be greater than zero.
cac:InvoiceLine/cac:Item/cac:ClassifiedTaxCategory[normalize-space(cbc:ID) = 'S'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT'] | cac:CreditNoteLine/cac:Item/cac:ClassifiedTaxCategory[normalize-space(cbc:ID) = 'S'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT'](cbc:Percent) > 0