Reason being it gets too complicated to account for it, as the tax rate changes according to stored tax credits. I like to make a comparison on earnings before tax, as you don't have to worry about this. The other thing is the tax that they pay gets added onto my profit/loss statement I lodge to the tax man, who taxes me at my peronal rate not company rate. Hence I find it simpler to work without tax, and pay it when I make the profit.
