Income tax is a tax that governments impose on the money you earn. It applies to wages, salaries, investment returns, business profits, and most other forms of income you receive during a year. In the United States, income taxes are collected at the federal level, and most states impose their own income tax on top of that. The federal system uses a progressive structure, meaning people who earn more pay a higher percentage on their upper tiers of income.
How Income Tax Works
The basic idea is straightforward: you add up the income you received during the year, subtract any deductions you qualify for, and pay a percentage of what’s left. That remaining amount is your taxable income. The percentage you owe depends on how much you earned and which tax bracket your income falls into.
Income doesn’t have to come as a paycheck. The IRS considers income to be money, property, goods, or services you receive. Even if you don’t get a tax form reporting it, you’re still required to include it on your return. Income is also considered taxable when you receive it, even if you don’t cash a check or use the funds right away. If someone pays a bill on your behalf, that counts as your income too.
What Counts as Taxable Income
The list of taxable income is broad. Most income is taxable unless a specific law exempts it. The major categories include:
- Employment income: Wages, salaries, bonuses, and employee benefits reported on your W-2.
- Self-employment and side income: Freelance work, independent contracting, gig work through apps, selling goods or services online, renting out personal property, royalties, and even bartering goods or services.
- Investment income: Capital gains (profit from selling an asset for more than you paid), stock dividends, interest earned on bank accounts or bonds, stock option exercises, and cryptocurrency transactions.
- Benefits and distributions: Retirement plan withdrawals, pension payments, annuities, unemployment benefits, some Social Security income, certain life insurance proceeds, and some survivor benefits.
- Other income: Canceled debts (if a lender forgives what you owe, the forgiven amount can be taxable), alimony payments received under older divorce agreements, court awards and legal damages, gambling winnings, prizes, and even certain scholarships.
Some income is excluded from taxation. Common examples include gifts you receive, most inheritances, life insurance death benefits paid to a beneficiary, and a portion of Social Security benefits for lower-income retirees. But the default rule is that income is taxable unless a specific provision says otherwise.
The Progressive Tax System
The federal income tax is progressive, which means the rate increases as your income rises. But a common misunderstanding is that moving into a higher bracket means all your income gets taxed at the higher rate. That’s not how it works. Only the income within each bracket gets taxed at that bracket’s rate.
For example, if you’re a single filer earning $60,000, you don’t pay 22% on the entire amount. Your first $12,400 is taxed at 10%, the next chunk up to $50,400 is taxed at 12%, and only the portion above $50,400 is taxed at 22%. This layered approach means your effective tax rate, the overall percentage of income you actually pay, is always lower than your top bracket rate.
The federal system currently has seven brackets, with rates of 10%, 12%, 22%, 24%, 32%, 35%, and 37%. The dollar thresholds for each bracket adjust periodically and vary based on your filing status (single, married filing jointly, head of household, etc.).
Not every tax system works this way. A proportional (or flat) tax charges the same percentage regardless of how much you earn. A regressive tax ends up taking a larger share of income from lower earners. Sales taxes are a common example of a regressive tax: everyone pays the same dollar amount on the same purchase, but that amount represents a bigger percentage of a lower income. The U.S. combines progressive income taxes with regressive taxes like Social Security payroll taxes. The net effect is that most Americans pay a roughly similar overall share of their income in total taxes.
Federal, State, and Local Layers
The federal government is not the only entity collecting income tax. Most states also levy their own income tax with separate rates and rules. Some states use a progressive bracket system similar to the federal model, while others apply a single flat rate to all income. Nine states impose no state income tax at all.
State tax rates and brackets vary widely, and your total tax burden depends in part on where you live and earn income. Some cities and counties add a local income tax on top of state and federal obligations, creating a third layer. Each level of government sets its own rules for what counts as taxable income, which deductions are allowed, and what credits are available, so your state return may look quite different from your federal return.
Where the Legal Authority Comes From
The federal government’s power to tax income comes from the Sixteenth Amendment to the Constitution, ratified in 1913. It states: “The Congress shall have power to lay and collect taxes on incomes, from whatever source derived.” Before that amendment, the Supreme Court had ruled in 1895 that a federal income tax on property-derived income was unconstitutional without being divided among the states based on population. The Sixteenth Amendment removed that restriction, clearing the way for a national income tax that applies uniformly based on what you earn rather than where you live.
How Income Tax Gets Collected
If you’re an employee, your employer withholds estimated income taxes from each paycheck throughout the year based on the information you provide on Form W-4. When you file your tax return, you compare the total tax you owe against what was already withheld. If too much was withheld, you get a refund. If too little was withheld, you owe the difference.
Self-employed workers, freelancers, and people with significant investment income typically don’t have taxes withheld automatically. Instead, they’re expected to make estimated tax payments quarterly. Missing these payments can result in penalty charges when you file your annual return.
The annual tax return is due in mid-April for most individual filers. On that return, you report all your income for the previous calendar year, claim any deductions and credits you’re eligible for, calculate your total tax liability, and settle up with the IRS. If you also owe state income tax, you generally file a separate state return around the same time.
Deductions and Credits Reduce What You Owe
Two key tools lower your income tax bill. Deductions reduce the amount of income that gets taxed. You can either take the standard deduction, a fixed dollar amount that varies by filing status, or itemize individual deductions like mortgage interest, charitable donations, and state taxes paid. Most filers take the standard deduction because it’s simpler and often larger than their itemized total.
Tax credits directly reduce the tax you owe, dollar for dollar, making them more valuable than deductions of the same size. A $1,000 deduction saves you whatever your marginal tax rate is on that $1,000 (so $220 if you’re in the 22% bracket). A $1,000 credit saves you a full $1,000 regardless of your bracket. Common credits include the child tax credit, the earned income tax credit for lower-income workers, and education credits for tuition expenses.