If you make ₦1,800,000 a year living in Nigeria, you will be taxed ₦455,000. That means that your net pay will be ₦1,345,000 per year, or ₦112,083 per month. Your average tax rate is 25.3% and your marginal tax rate is 31.5%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of ₦100 in your salary will be taxed ₦31.50, hence, your net pay will only increase by ₦68.50.
A ₦1,000 bonus will generate an extra ₦685 of net incomes. A ₦5,000 bonus will generate an extra ₦3,425 of net incomes.