Tusker

Hi, Can someone please help me with an issue. If I use gift cards the customer can choose an amount but at checkout there is VAT added to the amount. If I create a promotional code the voucher gets deducted from the price before VAT. and not from the total . All item prices are marked as VAT included. How can I sell Vouchers for an amount VAT included, or how can promo code vouchers be deducted from the total sum including VAT ?