The marginal tax rate is the rate applied to the last and highest portion of income in a progressive tax system. Earning more money does not mean your entire income is taxed at the new rate — only the portion above each bracket threshold is.

Misunderstanding this leads people to decline pay rises for fear of moving into a higher bracket, which is always financially irrational in progressive systems: net income always increases when gross increases. WorthOf's calculator shows the precise marginal rate for any salary in any of 50 countries.