The more you spend on a cashback card, the more you earn. However, some cards will offer different rates for different types of spending. For instance, one card may give you 1.5% cashback for spending in a supermarket, but 3.2% for spending in a petrol station. It's also possible for different rates to be given according to the amount you spend. For instance, you might get 2% cashback on expenditure up to £2,500, but 3% on anything spent above this mark. Similarly, some cards only offer cash back for certain stores, and others pay high rates for limited introductory periods.