Summary
If you make £18,243,680 a year living in United Kingdom, you will be taxed £8,785,237. That means that your net pay will be £9,458,443 per year, or £788,204 per month. Your average tax rate is 48.2% and your marginal tax rate is 48.3%. 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 £48.25, hence, your net pay will only increase by £51.75.
Bonus Example
A £1,000 bonus will generate an extra £518 of net incomes. A £5,000 bonus will generate an extra £2,588 of net incomes.