It's up to your bank to decide whether expiration matters, and they can vary their opinion by payment channel - expired card is more likely to be ok for paying

It's up to your bank to decide whether expiration matters, and they can vary their opinion by payment channel - expired card is more likely to be ok for paying a bill than it is for ordering from a web store. The merchant has no reliable way to learn whether the card expiration is wrong - the protocol has a card expired message but in practice banks use it for other errors too, and accept charges that should have expiration errors.