No. Look, you may be paying 29p, but that is less than the duty plus VAT on duty cost of the can, OK? As it stands, however, the supermarket must pay the cost of duty and VAT on that duty, i.e. 38p. They are selling that can at a loss, since they are charging less than they are obliged to pay in duty and tax on that duty. The only change will be that supermarkets etc will not be able to sell that can for lower than the cost of the duty and the VAT chargeable on that duty (which is the only VAT applicable). The government's tax take on that 29p can does not change since it is already, for duty and tax purposes, a 38p can.