Where cards reduce friction
Official visitor transport guidance says foreign-issued cards are accepted at rail ticket machines and counters, many express/intercity bus purchase points, taxis and selected booking services. Visit Seoul also provides foreign-language ATM and authorised exchange guidance.
Where cash still solves a real problem
The KTO’s 2026 transport guide labels ordinary T-money purchase and top-up as cash only for foreign-card holders. Markets and individual small merchants can also make cash useful, but the planner lets you choose that budget rather than imposing a generic daily amount.
The resilient setup
Carry two independently issued cards if possible, keep them separately, and obtain a staged KRW amount. Use the cash target as a planning ceiling, not a command to carry the full amount from day one.