The Federal Income Tax Calculation, Step by Step
Step 1: Total gross income — wages, freelance, interest, dividends, capital gains, rental income.
Step 2: Subtract above-the-line deductions — 401(k)/IRA contributions, HSA, student loan interest, self-employed health insurance, half of SE tax.
Step 3: Subtract the standard or itemized deduction
About 87% of taxpayers took the standard deduction in 2022, up from 70% before the Tax Cuts and Jobs Act doubled it in 2018. Source: Tax Policy Center (2023) — Source
For 2024: $14,600 (single), $21,900 (head of household), $29,200 (married filing jointly).
Step 4: Apply the progressive brackets — see our tax bracket calculator.
Step 5: Subtract tax credits — dollar-for-dollar liability reduction.
The Factors That Swing Your Liability Most
Filing status: A married couple filing jointly gets double the bracket thresholds and a larger standard deduction than two single filers.
Retirement contributions: The 401(k) limit for 2024 is $23,000 ($30,500 if 50+). Maxing out in the 22% bracket saves $5,060 in federal taxes alone.
Capital gains: Long-term gains are taxed at 0%, 15%, or 20%.
The 2024 long-term capital gains 0% rate applies to taxable income up to $47,025 for single filers. Source: IRS Rev. Proc. 2023-34 — Source
The Earned Income Tax Credit lifted 5.6 million people out of poverty in 2022, with an average credit of $2,541. Source: Center on Budget and Policy Priorities (2023) — Source
See also: income tax estimator, tax liability calculator, and the tax estimator guide.
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