Summary
If you make $51,609,996 a year living in New Zealand, you will be taxed $20,110,012. That means that your net pay will be $31,499,984 per year, or $2,624,999 per month. Your average tax rate is 39.0% and your marginal tax rate is 39.0%. 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 $39, hence, your net pay will only increase by $61.
Bonus Example
A $1,000 bonus will generate an extra $610 of net incomes. A $5,000 bonus will generate an extra $3,050 of net incomes.