Fixed amount discount vouchers to be applied in total invoice

[Miri Lukis]

Hello!!

I need to set coupons for a fixed amount (not a percentage) to be applied on the total amount of the invoice; ie after calculating taxes and shipping costs.

I do not want to apply it on the basis because then the VAT on products (10% in my case) is calculated over product price - coupon amount.

And I want it to be after the shipping because I do not offer free shipping, but if the coupon also covers a part, so customer do not have to pay 100% + 21% VAT.

Thank you very much in advance!!!