Income tax starts with your gross income, then subtracts deductions, then applies a tax rate based on your filing status and income bracket

Income tax calculation follows a fixed sequence. You begin with all the money you earned — your gross income. You then subtract certain amounts called deductions. What remains is your taxable income. The federal government then applies a tax rate to that taxable income based on which tax bracket you fall into. The result is the tax you owe. State and local taxes follow the same basic path but use different rates and rules.

The math itself is straightforward. The complexity comes from what counts as income, which deductions you can use, and how tax brackets work. This section walks through each step in order.

Key Takeaways

  • Gross income includes wages, self-employment earnings, investment income, and other money you received during the year.
  • You subtract either the standard deduction (a fixed amount based on your filing status) or itemized deductions (specific expenses you list) — whichever is larger.
  • Tax brackets are progressive, meaning different portions of your income are taxed at different rates, not your entire income at one rate.
  • The tax you owe depends on your filing status (single, married filing jointly, head of household, or married filing separately), which determines both your tax bracket and your standard deduction amount.

What counts as gross income

Gross income is every dollar you received that the IRS considers taxable. This includes your salary or wages from a job, tips, bonuses, and overtime pay. It also includes self-employment income if you run a business or freelance. Interest from savings accounts, dividends from stocks, rental income, and capital gains (profit from selling an asset) all count. Unemployment benefits, Social Security benefits (in some cases), and retirement account withdrawals are taxable income too.

Some money you receive is not taxable income. Gifts, inheritances, and life insurance payouts do not count. Certain scholarships and grants do not count if they pay for tuition or books. Workers' compensation and some disability payments are excluded. The key is whether the IRS has a rule that says that specific type of money is not taxable — if it does not, you count it.

Subtracting deductions to find taxable income

After you add up your gross income, you subtract deductions. The IRS lets you subtract either the standard deduction or itemized deductions — you choose whichever is larger, and you cannot use both.

The standard deduction is a fixed dollar amount that depends on your filing status and age. For the 2024 tax year, the standard deduction for a single filer under 65 is one amount; for a married couple filing jointly it is higher; for head of household it is different again. These amounts change each year. You do not have to list anything — you just subtract the number from your gross income.

Itemized deductions are specific expenses you paid during the year that the IRS allows you to deduct. These include mortgage interest, state and local taxes (up to a limit), charitable donations, and medical expenses above a certain threshold. You add up all your itemized deductions and subtract that total instead of the standard deduction — but only if that total is larger than the standard deduction for your filing status.

The result of gross income minus deductions is your taxable income. This is the number you use to calculate how much tax you owe.

How tax brackets determine your tax rate

Tax brackets are often misunderstood. Many people think that if you fall into the 22% bracket, you pay 22% on all your income. That is not how it works. The United States uses a progressive tax system, meaning different portions of your income are taxed at different rates.

Here is how it actually works: the IRS sets income ranges, and each range has its own tax rate. For example, in 2024, a single filer might pay 10% on the first $11,600 of taxable income, then 12% on income from $11,601 to $47,150, then 22% on income from $47,151 to $100,525, and so on. You move through these brackets as your income increases. Your marginal tax rate is the rate on your last dollar of income — the bracket you are currently in. Your effective tax rate is your total tax divided by your total taxable income, which is always lower than your marginal rate because of the progressive structure.

Tax brackets change every year and depend on your filing status. A single filer, a married couple filing jointly, and a head of household all have different bracket ranges and rates.

Filing status and how it affects your tax

Your filing status determines which tax brackets and standard deduction amount apply to you. The IRS recognizes four filing statuses: single, married filing jointly, married filing separately, and head of household.

Single means you are unmarried on December 31 of the tax year. Married filing jointly means you are married and file one return together — this status usually results in the lowest tax. Married filing separately means you are married but file two separate returns; this is rarely advantageous and usually results in higher total tax. Head of household means you are unmarried, paid more than half the household expenses, and had a dependent living with you for more than half the year — this status has tax brackets between single and married filing jointly.

Your filing status affects both your standard deduction and your tax brackets. A married couple filing jointly has a higher standard deduction and wider tax brackets than a single filer, which is why two people earning the same total income might owe different amounts depending on whether they are married and how they file.

Credits and how they reduce your final tax bill

After you calculate the tax owed based on your taxable income and tax bracket, you then subtract tax credits. A credit is different from a deduction. A deduction reduces your taxable income; a credit reduces your actual tax bill dollar for dollar.

Common credits include the Earned Income Tax Credit (EITC) for lower-income workers, the Child Tax Credit for parents, the American Opportunity Credit for students, and the Saver's Credit for people who contribute to retirement accounts. Some credits are refundable, meaning if the credit is larger than the tax you owe, you get the difference back as a refund. Others are non-refundable, meaning they can reduce your tax to zero but not below.

Credits are powerful because they reduce your tax dollar for dollar. A $1,000 credit saves you $1,000 in tax. A $1,000 deduction saves you tax only at your marginal rate — if you are in the 22% bracket, a $1,000 deduction saves you $220.

Self-employment tax and how it differs from income tax

If you are self-employed — you run your own business or freelance — you owe both income tax and self-employment tax. Self-employment tax covers Social Security and Medicare, the same programs that are deducted from a regular paycheck. If you work for an employer, your employer pays half of these taxes and you pay half. If you are self-employed, you pay both halves yourself.

Self-employment tax is calculated on your net self-employment income (your business income minus business expenses). The rate is 15.3% — 12.4% for Social Security and 2.9% for Medicare. You calculate this separately from your income tax, though both amounts end up on your tax return. You can deduct half of your self-employment tax as an adjustment to income, which lowers your taxable income slightly.

Self-employed people also have the option to deduct business expenses — rent, supplies, equipment, vehicle mileage, and other costs directly related to the business. These deductions reduce your net self-employment income and therefore reduce both your self-employment tax and your income tax.

State and local income tax calculations

Most states have their own income tax, and some cities do as well. State and local income taxes follow the same basic structure as federal tax — you calculate taxable income, apply a tax rate, and subtract credits — but the rates, brackets, and rules are different in each state.

Some states have a flat tax rate (the same percentage for everyone), while others use progressive brackets like the federal system. Some states do not have income tax at all — Alaska, Florida, Nevada, South Dakota, Tennessee, Texas, Washington, and Wyoming have no state income tax. New Hampshire and Tennessee tax only investment income, not wages.

State and local taxes are deductible on your federal return, but only up to $10,000 per year total (this limit is called the SALT cap). This means if you live in a high-tax state, you might not be able to deduct all your state and local taxes on your federal return.

Frequently Asked Questions

Why do I owe taxes if I had taxes withheld from my paycheck?

Withholding is an estimate. Your employer guesses how much tax you will owe for the year and withholds that amount from each paycheck. If they withhold too much, you get a refund. If they withhold too little, you owe more when you file. The actual tax you owe depends on your total income, deductions, credits, and filing status for the entire year — not just what was withheld.

Does a higher tax bracket mean I pay that rate on all my income?

No. Tax brackets are progressive. If you earn $60,000 and the brackets are 10% up to $11,600 and 12% from $11,601 to $47,150 and 22% from $47,151 and up, you pay 10% on the first $11,600, 12% on the next $35,550, and 22% on the remaining $12,850. You do not pay 22% on the entire $60,000.

What is the difference between a tax deduction and a tax credit?

A deduction reduces your taxable income. A credit reduces your tax bill directly. A $1,000 deduction might save you $220 in tax if you are in the 22% bracket. A $1,000 credit saves you $1,000 in tax no matter what bracket you are in.

Do I have to file taxes if I did not earn much money?

It depends on your income and filing status. If your gross income is below the standard deduction for your filing status, you generally do not have to file. However, if you had taxes withheld or you are self-employed, filing might get you a refund or let you claim credits you are owed.

How do I know which filing status to use?

Your filing status on December 31 of the tax year determines which one you use. If you are married, you can file jointly or separately. If you are unmarried but paid more than half your household expenses and had a dependent living with you, you can file as head of household. Otherwise, you file as single.