Transit IC card
What a transit IC card is
A transit IC card is a card you load with money in advance (known in Japan as charging) and then hold over a reader to pay your fare. PASMO and Suica are the best known cards in the Tokyo area, and thanks to a nationwide mutual-use arrangement the major transit IC cards behave the same way even when the card was issued in a different region. Alongside the physical card, there are versions you carry on a smartphone.
The mechanism is simple: every ride subtracts the fare from the balance recorded on the card. It does away with buying a ticket or counting out coins, which is why it has become the de facto standard way to pay for anyone who uses buses and trains day to day.
Using it on Toei buses
Toei Bus routes inside Tokyo's 23 wards charge a flat fare and collect it as you board at the front, so a single tap on the card reader built into the farebox finishes the payment. You do not need to tap again when you get off. Unlike cash there is no change to hand over, so boarding flows without interruption and there is no risk of keeping the people behind you waiting.
The one thing to watch is the balance. If it falls short of the fare, the tap returns an error and you have to settle in cash or top up on the spot, which costs time. Ways to add money on board a bus are limited, so the trick to comfortable use is to top up beforehand at a station ticket machine or a convenience store. If you ride buses every day, keeping a generous balance on the card saves worry.
How it differs from paying cash
Paying cash on a Toei bus means dropping the exact fare into the farebox. Large banknotes cannot always be changed, so coins or a ¥1,000 note are essential preparation. An IC card removes that preparation entirely, and even on a rainy day with one hand holding an umbrella you can board with a single tap.
Note too that IC card fares and cash fares can differ by a few yen, because card fares can be priced in 1-yen units. Services such as transfer discounts are sometimes designed on the assumption that you are paying by card, so see our article on Toei Bus fares and how to pay for the details of each payment method. Another point worth keeping in mind when you take a bus while traveling is that the routine varies by region and route: where the fare changes with distance, you tap both on boarding and on getting off.