If you make NT$ 8,000,000 a year living in Taiwan, you will be taxed NT$ 2,675,933. That means that your net pay will be NT$ 5,324,067 per year, or NT$ 443,672 per month. Your average tax rate is 33.5% and your marginal tax rate is 59.4%. 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$ 59.36, hence, your net pay will only increase by NT$ 40.64.
A NT$ 1,000 bonus will generate an extra NT$ 406 of net incomes. A NT$ 5,000 bonus will generate an extra NT$ 2,032 of net incomes.