I thought so too When I first rode the subway, it felt strange that they told me to tap my card when getting off. I don't know about buses, but for the subway you already paid when you entered, didn't you? I thought tapping when exiting was just a formality, like a button to open and close the doors. But if you forget once and just go out, then when you tap on another bus or the subway to transfer, the transfer discount isn't applied. ## To get the transfer discount, tap your card on the reader when you get off. The Korean transit card system is set up so that fares are discounted when you transfer from a bus to the subway or vice versa. You have to tap when you get off so the system recognizes "this person is transferring" and recalculates the fare on the next vehicle. If you don't tap, it's treated as a new trip instead of a transfer, so you'll be charged separately. ## If you made a mistake, do this If you tapped at the wrong station or exited without tapping, check at the fare adjustment machine inside the station or at the station office. You can also view your card history in your card issuer's app, so if a strange amount was charged, start checking there.