Unless the light blue card website has changed, I never had to pay for a voucher first. They just give you a discount code to get money off. For example: My other half normally uses the code for 20% of JD sports. If there is a shop i need to buy a present for a family member, I normally look on there to so if I can get a discount. You can get a free delivery pass from morrisons. You can link your card to the Asda reward card. When I worked through the pandemic you use to get free things from the supermarket as a thank you x
Some are vouchers but a lot are discount or money back like at Asda xx
If it’s from their voucher shop for things like food shopping, yes you’ll use your voucher to get the money off and then pay the difference