If there's one habit to leave at home, it's reaching for a tip. Korea doesn't have a tipping culture, and in most situations trying to leave one causes more confusion than goodwill.
Restaurants
The price on the menu is the price you pay, from a ₩3,000 kimbap roll to a high-end Gangnam dinner. Service isn't tipped separately — a 1979 law requires restaurants to display the final price, tax and any service charge included, which is exactly why tipping never took hold. Leaving cash on the table can genuinely prompt staff to chase you down assuming you forgot it.
Taxis
Pay the metered fare and that's it. Drivers don't expect anything extra, though rounding up or leaving ₩1,000–2,000 for help with heavy luggage is fine and won't feel awkward.
Hotels
The same applies to housekeeping and bellhops at most Korean-run hotels — it's not expected. International hotel chains catering heavily to Western guests are the one place where a small tip for exceptional service won't be unusual, but it's still optional.
Why
Workers are paid a standard wage rather than one that depends on tips to be liveable, so there's no economic expectation built into the interaction the way there is elsewhere. Save the won for the trip itself.