[BR-NG-12-GST-SG]-An Invoice that contains a GST breakdown group (BG-23) with a GST category code (BT-118) "NG" shall not contain an Invoice line (BG-25) where the Invoiced item GST category code (BT-151-GST) is not "NG".
BR-NG-12-GST-SG
/ubl:Invoice | /cn:CreditNote
(exists(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='GST']/cbc:ID[normalize-space(.) = 'NG']) and count(//cac:ClassifiedTaxCategory[normalize-space(cbc:ID) != 'NG'][cac:TaxScheme/normalize-space(upper-case(cbc:ID))='GST']) = 0) or not(cac:TaxTotal/cac:TaxSubtotal/cac:TaxCategory[cac:TaxScheme/normalize-space(upper-case(cbc:ID))='GST']/cbc:ID[normalize-space(.) = 'NG'])