Summary
If you make 618,799,992 원 a year living in South Korea, you will be taxed 252,919,553 원. That means that your net pay will be 365,880,439 원 per year, or 30,490,037 원 per month. Your average tax rate is 40.9% and your marginal tax rate is 47.9%. 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 47.88 원, hence, your net pay will only increase by 52.12 원.
Bonus Example
A 1,000 원 bonus will generate an extra 521 원 of net incomes. A 5,000 원 bonus will generate an extra 2,606 원 of net incomes.