[BR-103-GST-SG]- When providing Total Amount including GST in SGD, element ID must be set to the code value SGD
BR-103-GST-SG
cac:AdditionalDocumentReference[cbc:DocumentTypeCode]
(cbc:DocumentTypeCode='sgdtotal-incl-gst' and cbc:ID='SGD') or cbc:DocumentTypeCode != 'sgdtotal-incl-gst'