With a single T-money card you can pay for the subway, buses, and taxis, and transfers within 30 minutes are free of extra charge. Buy one right after landing at the convenience stores in Incheon Airport Terminals 1 and 2.
Buying and charging
Buy the card for 2,500 won at convenience stores like GS25, CU, and 7-Eleven or at subway stations, then top up anywhere from 10,000 to 90,000 won. Fares deduct automatically from the balance, so you don't need cash.
Using subway and bus
The base subway fare is 1,400 won, rising 100 won per 5km beyond 10km, with free transfers within 30 minutes. Stations and lines are labeled in English, Chinese, and Japanese, so you can get around without Korean, and Seoul buses are color-coded by route type.
Rush hours (7 to 9am and 6 to 8pm) are very crowded, so avoid them with large luggage.
A foreigner's master guide to buying, charging, transfers, and taxis