discount coupon to take off the VAT

I have a uk based site and need a voucher that takes off the VAT.

I tried a 17.5% off voucher but the tax is added to the base price so this does not work.

Baiscally I need to change my voucher so it DIVIDES the total price by 1.175 rather than take away 17.5%.

If you cna help me I would be very grateful.

Many thanks.

That would most likely require some very complex programming in a number of areas as it's just not how coupons work, and even if you deducted that amount from the total paid by the customer, your Zen Cart would still record 17.5% of what they have paid as being VAT.

Maybe if you could tell us more about the circumstances with which you are trying to deal, we might be able to advise a different solution.

Basically the products are medical come under the medical category which means they are exempt from VAT if the user has a condition.

There are 2 prices, the full price and a vat free price. My idea was to take off the vat with a voucher at the checkout after the user self-declares we send him a code which he redeems.

At the first level your Maths is wrong. To remove a 17.5% increase you would need to apply a voucher for 14.893617% not 17.5%.

An alternative to using vouchers would be to use Group Pricing. It's about the same amount of work for you, but saves the customer having to remember their voucher information each time. You would set up a group with a discount of 14.893617% and add customers who self-certificate to it.

However, both discounts and group pricing would still result in tax being calculated and presumably reported on your confirmation emails. I'll give some more thought to that to see if there's a way around that which doesn't involve programming work.