|Hi Jen, thanks for your reply. I guess its for all percentages really AUS and NZ|
I worked it out for the ex.GST amounts i.e.:
10% = total/1.1
15% = total/1.15
20% = total/1.2
But I still haven't worked out the simple equation to find the actual GST amount for 15 & 20% which is similar to the 10/11 equation...