Summary
If you make 27,720,160 원 a year living in South Korea, you will be taxed 3,991,667 원. That means that your net pay will be 23,728,493 원 per year, or 1,977,374 원 per month. Your average tax rate is 14.4% 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.