Message

[BR-S-07]-In a Document level charge (BG-21) where the Document level charge VAT category code (BT-102) is "Standard rated" the Document level charge VAT rate (BT-103) shall be greater than zero. 

Context
cac:AllowanceCharge[cbc:ChargeIndicator=true()]/cac:TaxCategory[normalize-space(cbc:ID)='S'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='VAT']
Test
(cbc:Percent) > 0
Usage
/ ubl:Invoice / cac:AllowanceCharge / cac:TaxCategory / cbc:Percent