Need to deduct Coupon value after VAT is added

[pwithers]

Hi,

I am designing a website selling mobility equipment www.a1mobilitysolutions.com

Customers who are registered disabled are entitled to VAT exempt mobility equipment. However customers who are not registered disabled will have to pay the VAT.

I have set up the VAT tax rates so the 20% VAT charge is applied to all equipment.

I have then set up a coupon that customers can use if they are VAT exempt.

However when they go to checkout, they see this:

Sub-Total: £650.00

Per Item (Best Way): £2.50

Discount Coupon: VATEXEMPT : -£130.00

VAT 20%: £104.00

Total: £626.50

In other words, it is applying the discount to the sub total, before the VAT is applied.

I need it so it applies the VAT first and then the discount, so in effect, the VAT will have been removed.

Any help is much appreciated. Am pretty new to all this.

[pwithers]

Anyone got any ideas on this? I need help please!

[pwithers]

I have searched everything in admin to solve this and searched through all the forum posts and cannot find anyone else trying to do what I have done, so I have decided to take a different route:

I will add a checkbox to the registration and sql db and alter the other relevent files to do this.

I will name this checkbox "vatexempt"

If this checkbox is ticked in the registration process then I would like the VAT to be removed automatically, if it is not then the VAT should be applied.

I know this will require a db enquiry to check whether the box is checked or not, but I do not know which file I will need to add this to. I also do not know where to put the "if checkbox is checked then add VAT, if not then dont" code, and am not entirely too sure how to write it.

My other idea was if the customer has checked the checkbox then just make all products tax free, in this case the VAT would not be added.

I do prefer my latest two ideas as it would be much simpler. The last one would be ideal but there doesnt seem to be anywhere I can add that rule.

Please help!