US Federal Income Tax is a tax levied by the United States Internal Revenue Service (IRS) on the annual earnings of individuals, corporations, trusts, and other legal entities. It operates on a progressive tax system, meaning that the tax rate increases as the taxable amount increases.
The US Federal Income Tax Formula
The calculation of federal income tax involves several steps:
Calculate taxable income:
Apply tax rates to each bracket of taxable income
Sum up the tax from each bracket:
Where:
TotalIncome is your gross income for the year
Deductions include standard or itemized deductions
BracketIncome is the portion of your income that falls within each tax bracket
BracketRate is the tax rate for each bracket
Step-by-Step Tax Calculation
Determine your filing status (single, married filing jointly, head of household)
Calculate your taxable income by subtracting deductions from your total income
Identify the tax brackets that apply to your filing status
Calculate the tax for each bracket your income falls into
Sum up the tax from each bracket to get your total federal income tax
Calculate your effective tax rate by dividing total tax by total income
Example Calculation
Let's calculate the federal income tax for a single filer with an annual income of $75,000 and standard deduction of $12,550 (2021 tax year):