Summary
If you make 43,800,000 원 a year living in South Korea, you will be taxed 7,508,220 원. That means that your net pay will be 36,291,780 원 per year, or 3,024,315 원 per month. Your average tax rate is 17.1% and your marginal tax rate is 22.7%. 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 22.66 원, hence, your net pay will only increase by 77.34 원.
Bonus Example
A 1,000 원 bonus will generate an extra 773 원 of net incomes. A 5,000 원 bonus will generate an extra 3,867 원 of net incomes.