Can I offer a discount on gift vouchers?

It is possible to offer a discount on Specific gift vouchers - that can be used to book only a specific service. Customers will have to use a promotion code, that you can set up in Marketing>Promotions, to get the discount. 

It is not possible to offer discounts on Generic gift vouchers - this is to prevent customers from using 2 promotions for the same booking - one when the gift voucher is purchased, and one when they make a booking.