Summary
If you make 25,587,293 원 a year living in South Korea, you will be taxed 3,526,477 원. That means that your net pay will be 22,060,816 원 per year, or 1,838,401 원 per month. Your average tax rate is 13.8% and your marginal tax rate is 21.8%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of 100 원 in your salary will be taxed 21.82 원, hence, your net pay will only increase by 78.18 원.
Bonus Example
A 1,000 원 bonus will generate an extra 782 원 of net incomes. A 5,000 원 bonus will generate an extra 3,909 원 of net incomes.