You can earn cash back on the credit card only if you make eligible purchases, while card issuers and even credit cards have different requirements for 'eligible purchases'. Many cash back credit cards only calculate local and overseas retail purchases, but not spending like installment amount, internet banking bill payment service, auto-pay service and Octopus automatic add value service. With the popularity of mobile payment, Apple Pay and Android Pay have been included in some credit cards' "eligible purchases". Please read and fully understand your credit card's terms and conditions to earn more cash back rewards.