Message

[BR-48-GST-SG]-Each GST breakdown (BG-23-GST) shall have a GST category rate (BT-119-GST), except if the Invoice is not subject to GST.

Context
cac:TaxTotal/cac:TaxSubtotal
Test
exists(cac:TaxCategory[cac:TaxScheme/cbc:ID='GST']/cbc:Percent) or (normalize-space(cac:TaxCategory[cac:TaxScheme/cbc:ID='GST']/cbc:ID)='')
Usage
/ ubl:Invoice / cac:TaxTotal / cac:TaxSubtotal / cac:TaxCategory / cbc:Percent
/ ubl:CreditNote / cac:TaxTotal / cac:TaxSubtotal / cac:TaxCategory / cbc:Percent