Summary
If you make 54,471,048 원 a year living in South Korea, you will be taxed 9,982,452 원. That means that your net pay will be 44,488,596 원 per year, or 3,707,383 원 per month. Your average tax rate is 18.3% and your marginal tax rate is 23.5%. 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 23.46 원, hence, your net pay will only increase by 76.54 원.
Bonus Example
A 1,000 원 bonus will generate an extra 765 원 of net incomes. A 5,000 원 bonus will generate an extra 3,827 원 of net incomes.