What Is Federal Income Tax? Brackets, Deductions & How It Works
Last updated 04/22/2026 by
Ante Mazalin
Edited by
Andrew Latham
Summary:
Federal income tax is a progressive tax levied by the U.S. government on individuals, corporations, trusts, and estates based on their taxable income — with higher rates applying to higher income levels.
The tax is administered by the IRS and funds the bulk of federal government spending.
- Progressive brackets: Income is taxed at increasing rates as it crosses thresholds — only dollars in each bracket are taxed at that rate, not your entire income.
- Deductions reduce taxable income: Taxpayers subtract either the standard deduction or itemized deductions from their income before calculating what they owe.
- Credits reduce tax owed: Tax credits — unlike deductions — cut your bill dollar-for-dollar after the tax has been calculated.
- Pay-as-you-go system: Most taxpayers pay throughout the year via paycheck withholding; self-employed workers make quarterly estimated payments.
Federal income tax touches nearly every financial decision an American makes — from how much of a raise you keep to whether a Roth or traditional retirement account makes more sense. Getting a clear picture of how it works doesn’t require an accounting degree; it mostly requires understanding a handful of terms that the IRS obscures with jargon.
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What is federal income tax?
Federal income tax is the primary revenue source for the U.S. government, generating roughly half of all federal revenue each year. Also referred to as FIT tax, it is administered by the Internal Revenue Service (IRS) under rules set by Congress. Congress sets the tax rules under its constitutional authority; the IRS collects and enforces them.
It applies to most forms of income — wages, salaries, tips, freelance earnings, rental income, investment gains, and business profits. Some income types, such as contributions to certain retirement accounts or interest from municipal bonds, receive preferential treatment or outright exemptions. For a side-by-side look at how it compares to what states collect, see federal vs. state tax.
How the progressive tax system works
The U.S. uses a progressive tax system — meaning different portions of your income are taxed at different rates. Your tax bracket describes the rate applied to your last dollar of income, not all of your income.
For example, a single filer earning $60,000 in 2025 does not pay 22% on the entire amount. They pay 10% on the first $11,925, 12% on income from $11,926 to $48,475, and 22% only on income from $48,476 to $60,000. For a full breakdown of all seven brackets for every filing status, see the federal tax rates guide.
| Tax Rate | Single Filers (2025) | Married Filing Jointly (2025) |
|---|---|---|
| 10% | $0 – $11,925 | $0 – $23,850 |
| 12% | $11,926 – $48,475 | $23,851 – $96,950 |
| 22% | $48,476 – $103,350 | $96,951 – $206,700 |
| 24% | $103,351 – $197,300 | $206,701 – $394,600 |
| 32% | $197,301 – $250,525 | $394,601 – $501,050 |
| 35% | $250,526 – $626,350 | $501,051 – $751,600 |
| 37% | Over $626,350 | Over $751,600 |
Brackets are adjusted annually for inflation, per the IRS inflation adjustments.
Key terms that determine what you owe
Gross income
Gross income is your total income from all sources before any adjustments, deductions, or exemptions. It includes wages, freelance income, rental income, dividends, capital gains, and most other forms of compensation.
Adjusted gross income (AGI)
AGI is gross income minus specific “above-the-line” deductions — contributions to traditional IRAs, student loan interest, self-employment taxes, and health savings account contributions, among others. Your adjusted gross income is the figure used to determine eligibility for many tax credits and deductions, making it one of the most consequential numbers on your return.
Taxable income
Taxable income is AGI minus either the standard deduction or your total itemized deductions — whichever is larger. The tax brackets are applied to this final figure, not your gross income.
Standard deduction vs. itemized deductions
Every taxpayer chooses between two methods to reduce their AGI before calculating tax:
- Standard deduction: A flat amount based on your filing status — $15,000 for single filers and $30,000 for married couples filing jointly in 2025.
- Itemized deductions: The sum of specific allowable expenses — mortgage interest, state and local taxes (capped at $10,000), charitable contributions, and unreimbursed medical expenses above 7.5% of AGI.
According to the IRS Statistics of Income, roughly 90% of taxpayers now take the standard deduction following the 2017 Tax Cuts and Jobs Act.
Tax credits vs. tax deductions
Deductions reduce your taxable income; credits reduce the actual tax you owe — dollar for dollar. A $1,000 deduction saves you $220 if you’re in the 22% bracket. A $1,000 credit saves you $1,000 regardless of your bracket.
- Earned Income Tax Credit (EITC): Up to $7,830 for low- to moderate-income workers with qualifying children in 2024.
- Child Tax Credit: Up to $2,000 per qualifying child under age 17, with up to $1,700 refundable.
- Child and Dependent Care Credit: Up to 35% of qualifying care expenses.
- American Opportunity Tax Credit: Up to $2,500 per year for the first four years of college.
- Retirement Savings Contributions Credit (Saver’s Credit): Up to 50% of contributions to qualifying retirement accounts for lower-income taxpayers.
How federal income tax is collected
Most employees never write a check to the IRS directly — their employer withholds estimated income tax from each paycheck based on the instructions provided on their Form W-4.
At tax time, you file a tax return (usually Form 1040) that reconciles what you paid against what you actually owed. If you overpaid, the IRS sends a tax refund. If you underpaid, you owe the balance.
Self-employed workers, landlords, and investors with significant unwithheld income must make quarterly estimated tax payments — in April, June, September, and January — or face an underpayment penalty at filing.
Federal income tax vs. other federal taxes
Federal income tax is separate from FICA taxes — the Social Security and Medicare payroll taxes withheld from every paycheck. FICA totals 7.65% for employees (6.2% Social Security + 1.45% Medicare), matched by employers. For a full comparison, see SuperMoney’s breakdown of payroll tax vs. income tax.
Capital gains tax is also distinct from ordinary income tax. Short-term capital gains (assets held one year or less) are taxed at ordinary income rates. Long-term capital gains (held more than one year) are taxed at preferential rates of 0%, 15%, or 20%.
Pro Tip
Your marginal tax rate (the rate on your last dollar of income) and your effective tax rate (actual taxes paid divided by total income) are very different numbers. A single filer in the 22% bracket typically pays an effective rate closer to 12–14% because the lower brackets apply to most of their income.
Filing deadlines and extensions
The federal income tax filing deadline is April 15 for most taxpayers. A six-month extension — filed using Form 4868 — pushes the deadline to October 15.
An extension to file is not an extension to pay. Any taxes owed are still due by April 15. Filing late with an unpaid balance triggers both a failure-to-file penalty (5% of unpaid tax per month, up to 25%) and interest on the outstanding amount.
Who does not pay federal income tax?
According to the Tax Policy Center, approximately 40% of U.S. households owe no federal income tax in a given year — primarily because their income falls below the standard deduction threshold, or refundable credits eliminate their liability entirely.
A single filer under 65 with no dependents and income below $15,000 in 2025 owes no federal income tax after taking the standard deduction. This does not exempt them from FICA taxes, which apply from the first dollar of wages.
Key takeaways
- Federal income tax is progressive — higher rates apply only to income above each bracket threshold, not your entire income.
- The 2025 brackets range from 10% to 37% for individuals, with seven total rate tiers.
- Taxable income = gross income minus above-the-line deductions (AGI) minus the standard deduction or itemized deductions.
- Tax credits reduce your bill dollar-for-dollar and are more valuable than deductions of the same amount.
- Roughly 90% of taxpayers take the standard deduction ($15,000 single / $30,000 married filing jointly in 2025).
- The filing deadline is April 15; extensions to file are available but don’t extend the payment deadline.
- About 40% of U.S. households owe no federal income tax in a given year due to low income or refundable credits.
Frequently asked questions
What is the difference between federal income tax and state income tax?
Federal income tax is collected by the IRS and funds federal programs. State income tax is a separate levy collected by individual states. Seven states have no income tax. For a detailed comparison, see SuperMoney’s guide to federal vs. state tax.
What is the difference between my tax bracket and my effective tax rate?
Your tax bracket (marginal rate) is the rate on your last dollar of income. Your effective tax rate is total taxes paid divided by total income — always lower than your bracket because lower-bracket rates apply to most of your income.
Do I have to file a federal income tax return?
Filing is required if your gross income exceeds the standard deduction for your filing status. For 2025, that threshold is $15,000 for single filers under 65. SuperMoney’s guide on when you start paying taxes covers the exact thresholds by age and filing status.
What happens if I don’t pay federal income taxes?
Failing to pay triggers interest (currently around 8% annually) and a failure-to-pay penalty of 0.5% per month, up to 25%. Willful tax evasion is a federal crime carrying fines up to $250,000 and up to five years in prison.
How are capital gains taxed differently from ordinary income?
Short-term capital gains (held one year or less) are taxed at your marginal rate. Long-term capital gains (held more than one year) are taxed at 0%, 15%, or 20% depending on taxable income.
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