A top-up is a payment that you can make with a personal debit or credit card to make a purchase that costs more than your available allowance. The minimum top-up amount is £0.30. If the amount needed to top-up is less than £0.30, then you’ll either be required to add more items to increase the top-up amount above £0.30 or remove items from your cart so that your order total falls within your allowance.