Do I need to be careful how I use the card when paying?
Most of us keep our cards in some sort of wallet and the temptation is to tap the wallet on the payment terminal. If you have more than one card in your wallet, in theory you could be charged twice. For example, if you’re in London using an Oyster travel card, your credit or debit card could also be charged.
However, banks do use technology that should prevent this happening, and only one card should be charged. In the case of Oyster, that will usually take priority if it’s presented along with another card. There’s a simple way to avoid this issue though – take out the Oyster card out and present it properly to the terminal.