Summary
If you make 392,080,000 원 a year living in South Korea, you will be taxed 147,691,333 원. That means that your net pay will be 244,388,667 원 per year, or 20,365,722 원 per month. Your average tax rate is 37.7% and your marginal tax rate is 45.8%. 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 45.83 원, hence, your net pay will only increase by 54.17 원.
Bonus Example
A 1,000 원 bonus will generate an extra 542 원 of net incomes. A 5,000 원 bonus will generate an extra 2,709 원 of net incomes.