Summary
If you make 343,200,000 원 a year living in South Korea, you will be taxed 125,718,327 원. That means that your net pay will be 217,481,673 원 per year, or 18,123,473 원 per month. Your average tax rate is 36.6% and your marginal tax rate is 44.7%. 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 44.65 원, hence, your net pay will only increase by 55.35 원.
Bonus Example
A 1,000 원 bonus will generate an extra 554 원 of net incomes. A 5,000 원 bonus will generate an extra 2,768 원 of net incomes.