Summary
If you make 521,040,000 원 a year living in South Korea, you will be taxed 206,944,114 원. That means that your net pay will be 314,095,886 원 per year, or 26,174,657 원 per month. Your average tax rate is 39.7% and your marginal tax rate is 46.2%. 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 46.17 원, hence, your net pay will only increase by 53.83 원.
Bonus Example
A 1,000 원 bonus will generate an extra 538 원 of net incomes. A 5,000 원 bonus will generate an extra 2,692 원 of net incomes.