To obtain your marginal tax rate, simply go to the online tax calculator for your canton.
Enter your personal details (including whether you are married, with or without children, etc.) and your current taxable income and then enter the amount of tax you have to pay according to the calculator.
You repeat this via the online tax calculator for the direct federal tax portion.
Then repeat these two calculations with your new taxable in- come, for example, if your salary is increased by CHF 1'000.
Finally, calculate the rate using the following formula: (new tax - current tax) / (new taxable income - old taxable income) = marginal tax rate
With a concrete example, this gives:
- Current income = CHF 100'000/year
- Current taxes = CHF 20'000/year
- New income = CHF 105'000/year
- New taxes = CHF 22'000/year
- Marginal tax rate = 40% (because (CHF 22'000 - CHF 20'000) / (CHF 105'000 - CHF 100'000) = 0.4)