Federal income tax is the tax the U.S. government charges on the annual earnings of individuals and businesses, and it funds most federal operations. For individuals, the tax uses a progressive rate structure with seven brackets for 2026, running from 10% on the lowest earnings to 37% on income above $640,600 for single filers.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Domestic corporations pay a flat 21%.2Office of the Law Revision Counsel. 26 U.S.C. 11 – Tax Imposed Most workers pay throughout the year through paycheck withholding and reconcile the total on a return filed by April 15.
Who Has to Pay
U.S. citizens owe federal income tax on their worldwide income, no matter where they live. An American working in London or Tokyo still files a U.S. return and reports those foreign earnings.3Internal Revenue Service. U.S. Citizens and Residents Abroad – Filing Requirements
Resident aliens face the same worldwide obligation. You qualify as a resident alien for tax purposes if you hold a green card or meet the substantial presence test, which counts physical days in the country across a three-year period.4Internal Revenue Service. Substantial Presence Test Nonresident aliens have a narrower obligation, generally owing tax only on income connected to a U.S. trade or business or sourced from U.S. assets, such as wages earned while working in the country or interest from domestic investments.5Internal Revenue Service. Determining an Individual’s Tax Residency Status
What Counts as Income
The tax code casts an intentionally wide net. Under 26 U.S.C. § 61, gross income includes all income from whatever source derived unless another provision specifically excludes it.6Office of the Law Revision Counsel. 26 U.S.C. 61 – Gross Income Defined Wages and salaries are the biggest piece for most people, but the statute also reaches business profits, gains from selling property, interest, rents, royalties, dividends, annuities, and pensions. Less obvious items count too: gambling winnings, canceled debt, and income from a side business.
Some receipts are excluded by statute. Gifts and inheritances aren’t taxed to the recipient, though any later income those assets generate is.7Office of the Law Revision Counsel. 26 U.S.C. 102 – Gifts and Inheritances Life insurance proceeds paid because of the insured person’s death are generally tax-free to the beneficiary.8Office of the Law Revision Counsel. 26 U.S.C. 101 – Certain Death Benefits Disability insurance benefits are excluded when you paid the premiums yourself with after-tax dollars.9Internal Revenue Service. Life Insurance and Disability Insurance Proceeds Certain employer-provided health benefits and qualified scholarships used for tuition are excluded too.
How the Brackets Actually Work
For the 2026 tax year, seven brackets apply to individual filers:1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
- 10%: up to $12,400 (single) or $24,800 (married filing jointly)
- 12%: over $12,400 (single) or $24,800 (married filing jointly)
- 22%: over $50,400 (single) or $100,800 (married filing jointly)
- 24%: over $105,700 (single) or $211,400 (married filing jointly)
- 32%: over $201,775 (single) or $403,550 (married filing jointly)
- 35%: over $256,225 (single) or $512,450 (married filing jointly)
- 37%: over $640,600 (single) or $768,700 (married filing jointly)
A common misconception trips people up. Moving into a higher bracket does not mean all your income gets taxed at that rate. Only the dollars falling within each bracket are taxed at that bracket’s rate. A single filer earning $60,000 pays 10% on the first $12,400, 12% on the amount up to $50,400, and 22% only on the remaining amount above $50,400. Your effective rate, the overall percentage you actually pay, is always lower than your top bracket.
Deductions and Credits
Two mechanisms reduce what you owe, and the difference between them is worth real money.
A deduction lowers your taxable income before the rates apply. Most filers take the standard deduction rather than itemizing. For 2026, the standard deduction is $16,100 for single filers and married filing separately, $32,200 for married filing jointly, and $24,150 for head of household.1Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Itemizing makes sense only when deductible expenses like mortgage interest, state and local taxes (capped at $10,000), and charitable contributions exceed the standard amount. For most filers they don’t, which is why roughly 90% of returns use the standard deduction.
Credits are more valuable dollar-for-dollar because they reduce the tax itself, not the income used to calculate it. A $1,000 deduction saves you $220 if you’re in the 22% bracket. A $1,000 credit saves you the full $1,000.
Credits come in two flavors. A nonrefundable credit can bring your tax to zero but no further. A refundable credit can push the tax below zero and generate a refund even when you owed nothing. Widely claimed credits include the Child Tax Credit (up to $2,200 per qualifying child for 2026, with up to $1,700 refundable), the Earned Income Tax Credit for lower-income workers, and the American Opportunity Tax Credit for college expenses (up to $2,500 per year, partially refundable).10Internal Revenue Service. Refundable Tax Credits
Payroll Taxes on Top of Income Tax
Federal income tax isn’t the only federal tax on your earnings. Most workers also pay FICA taxes, which fund Social Security and Medicare. For 2026, employees pay 6.2% of wages toward Social Security on earnings up to $184,500, plus 1.45% toward Medicare on all wages with no cap.11Social Security Administration. Contribution and Benefit Base Employers match those amounts.
Self-employed individuals pay both halves, for a combined 15.3% (12.4% Social Security plus 2.9% Medicare) on net self-employment income. They can deduct half of that self-employment tax when calculating adjusted gross income, which partially offsets the double burden.
High earners face an additional 0.9% Medicare surtax on wages or self-employment income above $200,000 for single filers and $250,000 for married couples filing jointly.12Internal Revenue Service. Questions and Answers for the Additional Medicare Tax Employers do not match this surcharge.
How You Actually Pay
Paycheck Withholding
Most employees never write a check to the IRS. Federal law requires employers to deduct and withhold income tax from wages based on IRS tables, using the information you provide on Form W-4.13Office of the Law Revision Counsel. 26 U.S.C. 3402 – Income Tax Collected at Source When you start a job or your financial situation changes, updating your W-4 adjusts how much comes out. Getting this right matters. Too little withheld and you owe in April, possibly with penalties; too much and you’ve given the government an interest-free loan for a year.
Estimated Payments
If you earn income that isn’t subject to withholding — freelance work, rental income, investment gains — you may need to make quarterly estimated tax payments. The IRS generally requires them if you expect to owe at least $1,000 after subtracting withholding and refundable credits.14Internal Revenue Service. Estimated Tax Payments are due April 15, June 15, September 15, and January 15 of the following year. Underpaying can trigger a penalty even if you eventually get a refund when you file.
Filing the Return
Individual taxpayers file on Form 1040. Taxpayers 65 and older can use Form 1040-SR, which is functionally identical but formatted for easier reading.15Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return The filing deadline for the 2025 tax year is April 15, 2026.16Internal Revenue Service. IRS Opens 2026 Filing Season
If you need more time, filing Form 4868 or simply making an electronic tax payment gives you an automatic six-month extension, pushing the deadline to October 15, 2026.17Internal Revenue Service. Application for Automatic Extension of Time to File U.S. Individual Income Tax Return An extension to file is not an extension to pay. Interest and possible penalties still accrue on any unpaid balance after April 15.
What Happens If You File or Pay Late
Filing late carries a penalty of 5% of the unpaid tax for each month or partial month the return is overdue, up to a maximum of 25%.18Internal Revenue Service. Failure to File Penalty Paying late triggers a separate penalty of 0.5% per month on the unpaid balance, also capped at 25%.19Internal Revenue Service. Failure to Pay Penalty Both can run at the same time, and interest accrues on top of them. Because the failure-to-file penalty is ten times steeper than the failure-to-pay penalty, the practical rule is simple: if you can’t afford to pay, file the return anyway.
Willful evasion is a different tier. Willful tax evasion is a felony carrying a fine of up to $100,000 ($500,000 for corporations) and up to five years in prison.20Office of the Law Revision Counsel. 26 U.S.C. 7201 – Attempt to Evade or Defeat Tax Willful failure to file is a misdemeanor punishable by a fine of up to $25,000 and up to one year in prison.21Office of the Law Revision Counsel. 26 U.S.C. 7203 – Willful Failure to File Return, Supply Information, or Pay Tax The key word in both statutes is “willfully.” Honest mistakes and inability to pay don’t trigger criminal prosecution. The IRS pursues these cases when someone actively conceals income, files fraudulent returns, or deliberately ignores filing obligations across multiple years.
If You Disagree With the IRS
When the IRS examines your return and proposes changes, you don’t have to accept them. You can request a review through the IRS Independent Office of Appeals by filing a written protest, generally within 30 days of the notice.22Internal Revenue Service.