Message

Element 'cbc:ID' MUST contain value 'VAT'.

Context
/ubl:OrderChange/cac:AllowanceCharge/cac:TaxCategory/cac:TaxScheme/cbc:ID
Test
normalize-space(text()) = 'VAT'
Usage
/ ubl:OrderChange / cac:AllowanceCharge / cac:TaxCategory / cac:TaxScheme / cbc:ID