What is the math formula for federal income tax?
There is no single formula. Beause there are 5 filing statuses, there would be a minimum of 5 formulae. The equation would be a “step function” becasue the rate of tax changes at certain points (amounts of taxable income.) If you want to figure it yourself the break points for each tax bracket by filing status is shown in Schedules at the end of the tax tables in the 1040 Instruction booklet. However, it is not that simple. Each type of income (earned, capital, investment, passive, etc) has different rules that have an impact on whether and how much is taxable (or deductible). Moreover, deductions tend to phase out or drop off as income increases. Then, once tax is figured another calculaton for Alternative Minimum Tax comes into play that, which in some cases makes the regular tax calculation partially or entirely moot. Finally, once INCOME tax is figured, it can be reduced by credits, which have their own calculations and limitations. And that does not include other taxes shown on th
