How tax routes:
- Region = Local → CGST + SGST. Central → IGST. Driven by the TaxCategory percentage on each item.
- Transaction Type = Stock Transfer or Import → forces 0% tax on the entire purchase. Other runs normal Region split.
- No Tax Posting = report-filter flag only. Doesn't affect tax math.
- Reverse Charge = buyer pays GST directly to government (B2B GTA, lawyer fees, import services).