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Four illustrated students reading and learning. Income Tax.

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Beginner lesson · U.S. taxes · 5 minute read

Income tax, one layer at a time.

Understand what gets taxed, why brackets work in layers, and what the numbers on your paycheck actually mean.

Last reviewed October 9, 2026 · Illustrative examples, unless a tax year is specified.

1. What is income tax?

Income tax is a tax on income, such as money you earn from work. Start with one distinction: your earnings, your taxable income, and your take-home pay are different numbers.

EarningsWhat you makeBefore payroll deductions.
Taxable incomeWhat gets taxedAfter applicable adjustments and deductions.
Take-home payWhat arrivesAfter withholding and other payroll deductions.

2. Brackets work in layers

Federal income tax doesn't apply your highest bracket's rate to every dollar. Each layer of taxable income has its own rate. Your marginal rate is the rate on your next dollar of taxable income. An overall rate compares total tax with an income amount.

A made-up example: Imagine a system taxing the first $10,000 at 10% and the next $20,000 at 20%. With $30,000 of taxable income, the tax is $1,000 + $4,000 = $5,000. That's 16.7% of taxable income, even though the top layer is taxed at 20%.

These brackets are invented for learning. Actual federal brackets depend on filing status and tax year. Check the IRS brackets or try our visual example.

3. Deductions and credits do different jobs

A deduction reduces taxable income. A credit reduces tax owed. Eligibility and limits vary; some credits are refundable.

Simplified comparison: If a $1,000 deduction removes income that would have been taxed at 20%, it saves $200 in tax. A fully usable $1,000 credit reduces tax by $1,000. This example assumes the entire deduction falls in the same bracket.

Explore credits and deductions at the IRS ↗

4. Withholding is a payment toward your tax

Federal income tax withholding is money your employer sends to the IRS from your paycheck. It's a payment during the year, not a separate extra income tax. Your return works out your annual tax and compares it with payments and applicable credits.

A refund generally means payments and refundable credits exceed your tax. If they fall short, you may owe a balance. Other paycheck deductions, including Social Security, Medicare, insurance, and retirement contributions, are separate from federal income tax withholding.

Learn about withholding at the IRS ↗

5. Federal and state rules are separate

State and local income tax rules depend on your location and circumstances. Don't assume a federal rule automatically applies to a state return. USAGov helps you find your state tax agency.

Before looking up a rate: Identify the tax year, filing status, type of income, and government involved. A current-year paycheck and a return for last year's earnings are different contexts.

Keep learning from official sources

Check your understanding

You reach a higher federal bracket. What gets the higher rate?

Choose an answer.