How the margin is worked out
The selling price is the MRP less your discount. Take the GST out of it to get the sale value, then subtract your purchase rate. GST on the purchase is not a cost, because it comes back as input credit.
- Sale without GST = selling price ÷ (1 + GST)
- Margin = sale without GST − purchase rate
- Margin on sale = margin ÷ sale without GST