Message

The VAT category percentage MUST be provided if the VAT category code is standard.

Context
//cac:TaxSubtotal[cac:TaxCategory/cac:TaxScheme/cbc:ID = 'VAT']
Test
(cac:TaxCategory/cbc:Percent) or not(normalize-space(cac:TaxCategory/cbc:ID) = 'S')
Usage
/ ubl:Invoice / cac:AllowanceCharge / cac:TaxCategory / cbc:Percent
/ ubl:Invoice / cac:TaxTotal / cac:TaxSubtotal / cac:TaxCategory / cbc:Percent
/ ubl:Invoice / cac:InvoiceLine / cac:Item / cac:ClassifiedTaxCategory / cbc:Percent