If you make NT$ 2,000,000 a year living in Taiwan, you will be taxed NT$ 303,022. That means that your net pay will be NT$ 1,696,978 per year, or NT$ 141,415 per month. Your average tax rate is 15.2% and your marginal tax rate is 21.4%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of NT$ 100 in your salary will be taxed NT$ 21.41, hence, your net pay will only increase by NT$ 78.59.
A NT$ 1,000 bonus will generate an extra NT$ 786 of net incomes. A NT$ 5,000 bonus will generate an extra NT$ 3,930 of net incomes.