Federal income tax is a tax on the money you earn, collected by the U.S. Internal Revenue Service (IRS) and used to fund federal government operations

When you work, a portion of your paycheck goes to federal income tax before you receive it. Your employer withholds this amount and sends it to the IRS on your behalf. The tax rate depends on how much you earn — people who earn more pay a higher percentage. At the end of the year, you file a tax return to report all your income and either get money back (a refund) if too much was withheld, or pay more if too little was taken out.

Federal income tax is different from Social Security and Medicare taxes, which also come out of your paycheck but fund those specific programs. It is also separate from state and local income taxes, which some states and cities collect in addition to the federal tax.

Key Takeaways

  • Federal income tax is withheld from your paycheck by your employer and sent to the IRS, with the rate depending on your total annual income.
  • The U.S. uses a progressive tax system, meaning higher earners pay a higher percentage of their income in tax than lower earners.
  • You file a tax return each year to report your income and either receive a refund or pay additional tax owed.
  • Self-employed people and those with investment income must calculate and pay federal income tax themselves, usually in quarterly installments.

How the tax brackets work

The U.S. tax system uses tax brackets, which means your income is taxed at different rates depending on how much you earn. You do not pay one flat rate on all your income. Instead, each portion of your income falls into a bracket with its own rate.

For example, if the first bracket covers income up to $11,000 at 10%, the next bracket covers $11,001 to $44,725 at 12%, and so on, your first $11,000 is taxed at 10%, and any income above that is taxed at the next rate. The brackets change each year and vary depending on whether you file as single, married filing jointly, head of household, or another status. You can find the current year's brackets on the IRS website or through a tax software program.

This system is called progressive taxation because the percentage you pay increases as your income increases. A person earning $30,000 pays a lower overall percentage than a person earning $100,000.

What income counts toward federal tax

Federal income tax applies to most types of income you receive. This includes wages from a job, self-employment income, tips, interest from savings accounts, dividends from investments, rental income, and income from side work or freelancing. Some income is taxed differently or not at all — for instance, certain types of interest (like municipal bonds) and some government benefits are not subject to federal income tax.

When you file your tax return, you report all sources of income for the year. Your employer provides a W-2 form showing wages and taxes withheld. If you are self-employed or have other income, you may receive a 1099 form or need to report it yourself. The IRS matches what you report against what employers and financial institutions report, so underreporting income can trigger an audit.

How withholding works during the year

When you start a job, you complete a W-4 form that tells your employer how much federal income tax to withhold from each paycheck. The amount depends on your income level, whether you have dependents, and whether you have other jobs or income sources. If you withhold too much, you get a refund when you file your return. If you withhold too little, you owe money.

You can change your W-4 at any time during the year — for instance, if you get a raise, get married, have a child, or take a second job. Adjusting your withholding mid-year can help you avoid a large refund or a large bill at tax time. Self-employed people do not have an employer to withhold tax, so they must pay estimated quarterly taxes four times per year based on what they expect to earn.

Deductions and credits that reduce your tax

You do not pay federal income tax on your entire income. The tax code allows you to subtract certain amounts (called deductions) before calculating your tax. Most people use the standard deduction, which is a fixed amount set by the IRS each year. For 2024, the standard deduction is $13,850 for single filers and $27,700 for married couples filing jointly, though these amounts change annually.

Some people instead itemize deductions, meaning they list specific expenses like mortgage interest, property taxes, or charitable donations. Itemizing only makes sense if your total deductions exceed the standard deduction. Tax credits are different from deductions — they directly reduce the tax you owe dollar-for-dollar. Common credits include the Earned Income Tax Credit (EITC) for lower-income workers and the Child Tax Credit for parents.

Filing your tax return and getting a refund

You must file a federal income tax return by April 15 each year (or the next business day if April 15 falls on a weekend) to report your income and claim any refund or pay any tax owed. You file using IRS Form 1040 and any supporting schedules. Many people use tax software, hire a tax preparer, or use free filing services offered by the IRS and nonprofits.

When you file, the IRS compares what you report against what your employer and financial institutions reported. If you overpaid through withholding, you receive a refund — typically within a few weeks if you file electronically and request direct deposit. If you underpaid, you owe the difference and may face penalties and interest if the amount is significant.

Who does not have to file

Not everyone must file a federal income tax return. If your income is below a certain threshold (which depends on your age and filing status), you generally do not have to file. For 2024, a single person under 65 with income below $13,850 does not have to file. However, if you had taxes withheld from your paycheck, you should file anyway to get your refund.

Students, dependents, and people with very low income should check the IRS website or use the IRS interactive tool to determine whether they must file. Even if you are not required to file, you may want to file to claim the Earned Income Tax Credit or other refundable credits that result in a refund.

Frequently Asked Questions

What happens if I do not file a tax return?

If you owe tax and do not file, the IRS can assess penalties and interest on the unpaid amount. If you are due a refund and do not file, you simply do not receive it — the money stays with the government. The IRS can also pursue collection actions if the debt is large enough.

Can I change my W-4 if I think I am withholding the wrong amount?

Yes. You can submit a new W-4 to your employer at any time to adjust your withholding. This is useful if your income changes, you get married or divorced, have a child, or take on additional jobs. Adjusting mid-year can help you avoid a large refund or bill at tax time.

What is the difference between a refund and a credit?

A refund is money the IRS returns to you because you overpaid through withholding. A credit is a reduction in the tax you owe. A refundable credit can result in a refund if it exceeds your tax liability, while a non-refundable credit can only reduce your tax to zero.

Do I have to pay federal income tax on all my income?

Most income is subject to federal income tax, but some types are not — such as certain government benefits, gifts, and municipal bond interest. You report all income on your return, and the IRS determines what is taxable. When in doubt, include it and let the tax code determine the treatment.