If you make 1,200,000 kr a year living in Norway, you will be taxed 420,805 kr. That means that your net pay will be 779,195 kr per year, or 64,933 kr per month. Your average tax rate is 35.1% and your marginal tax rate is 46.4%. This marginal tax rate means that your immediate additional income will be taxed at this rate. For instance, an increase of 100 kr in your salary will be taxed 46.40 kr, hence, your net pay will only increase by 53.60 kr.
A 1,000 kr bonus will generate an extra 536 kr of net incomes. A 5,000 kr bonus will generate an extra 2,680 kr of net incomes.