Is income from derivatives trading taxed?

Yes. According to the National Tax Service, income from trading derivatives based on domestic or foreign stock indices, contracts for difference (CFDs), equity-linked warrants (ELWs), overseas exchange-traded derivatives and the like is subject to capital gains tax.

The rate under the Income Tax Act is 20%, which may be lowered by Enforcement Decree for purposes such as fostering the capital market. For derivatives, there is no preliminary return; you file a final return and pay for the whole year in May of the following year.