Showing VAT as 17.5 % of the revised total

[Guest]

Hi,

 

I would like some advice regarding VAT and discount coupons

 

I want the total payable to be the subtotal minus the value of the voucher and the tax to be in relation to te revised total (not the pre discount amount)

 

I have tried trial and error but im getting nowhere.

 

Any help on setting this up would be appreciated.