Summary
If you make 86,856,636 원 a year living in South Korea, you will be taxed 18,634,116 원. That means that your net pay will be 68,222,520 원 per year, or 5,685,210 원 per month. Your average tax rate is 21.5% and your marginal tax rate is 28.6%. 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 28.64 원, hence, your net pay will only increase by 71.36 원.
Bonus Example
A 1,000 원 bonus will generate an extra 714 원 of net incomes. A 5,000 원 bonus will generate an extra 3,568 원 of net incomes.