How does Korean income tax work for foreigners?

Korean income tax for foreigners runs on a progressive rate from 6% to 45% depending on income brackets. If you've lived in Korea less than 5 years you can also opt for a flat 19% rate, which sometimes works out better for higher earners.

Your employer withholds tax monthly through 원천징수. The annual reconciliation (연말정산) happens in February for salaried workers and balances any over- or under-payment. Freelancers and people with extra income file 종합소득세 every May through Hometax (hometax.go.kr) which has an English mode. Tax treaties with the US, Canada, UK, Australia and many EU countries prevent double taxation. For complex situations a tax accountant specializing in foreigners runs 300,000 to 800,000 won and is worth it the first year.