What is Income Tax?

Income tax is tax charged on income you receive or realize during the year, covering wages, self-employment profit, interest, dividends, taxable retirement distributions, and most other income the law does not specifically exclude. In the United States it is charged in layers: a federal tax, an income tax in most states, and in some places a local one as well.

For many households it is one of the largest lifetime costs, which makes the rules governing it worth understanding rather than delegating entirely.

What Gets Taxed

Not all income is treated alike, and the differences matter more than the headline rate.

Ordinary income covers wages, salary, bonuses, self-employment profit, interest, rents, and taxable distributions from pre-tax retirement accounts. It is taxed at the bracket rates, from 10% up to 37%.

Long-term capital gains and qualified dividends are taxed on a separate, lower schedule of 0%, 15%, and 20%. Collectibles and unrecaptured depreciation on real estate sit outside it, at up to 28% and 25% respectively.

The two qualify differently. A capital gain needs an asset held more than a year. A dividend generally needs the stock held more than 60 days within a 121-day window around the ex-dividend date, so holding period matters for both but means different things.

That gap between the ordinary and preferential schedules is why the character of income, not just the amount, drives so much tax planning. A capital gain realized after twelve months and one realized after eleven are taxed very differently.

Some income is not taxed at all, including Roth withdrawals meeting the qualification rules, most municipal bond interest, and a portion of Social Security benefits depending on total income.

From Gross Income to Tax Owed

The calculation runs in a fixed order, and each step does something different.

Start with total income, then subtract deductions to reach taxable income. Most filers take the standard deduction, $16,100 for a single filer and $32,200 for a married couple filing jointly in 2026, rather than itemizing. Pre-tax retirement contributions are accounted for before taxable income is set, though by different routes: workplace deferrals reduce the wages reported on your W-2, while a deductible IRA contribution is an adjustment on the return. The first dollars of a deduction save tax at your marginal rate; if it crosses a bracket boundary, the remainder saves at the lower rate.

Apply the bracket schedule to taxable income to get the tax. Then subtract credits, which come off the tax itself rather than off income. That is the structural difference between the two: a deduction is worth whatever marginal rate it displaces, while a credit is worth its face value, up to the amount you can use. A nonrefundable credit cannot take your tax below zero; a refundable one pays out the excess.

Income Tax Is Not the Only Layer

Earned income also carries payroll tax for Social Security and Medicare, split between employee and employer, with no standard deduction shielding it. It starts at the first dollar of covered wages, though some compensation is excluded from that base, including certain cafeteria-plan benefits and health savings account contributions made through payroll. Retirement account withdrawals are exempt from payroll tax, so the total rate on a dollar of wages and a dollar of pension income can differ substantially even when the income tax bracket is identical.

State treatment varies widely: some states levy no income tax, some tax at a flat rate, and some run their own graduated schedules. A few exempt retirement income specifically, which is a real factor in where people choose to retire.

Because the layers stack differently on different kinds of income, the combined rate is easier to read from a projection than to assemble by hand. The tax analytics page breaks a projected year into federal, state, and local components.

Income Tax Across a Retirement Plan

Working years tend to have a single dominant income source and a fairly predictable rate. Retirement is different, because you have some control over which accounts the money comes from and therefore over the rate you pay.

The low-income window between leaving work and the start of Social Security and required minimum distributions is where most of the leverage sits. Filling the lower brackets deliberately in those years, through Roth conversions or realizing gains, can cost less than letting balances grow and taking larger distributions at a higher rate later. The tradeoff runs over decades, so a year-by-year view tends to understate it.

Frequently Asked Questions

How is income tax calculated? Subtract deductions from total income to get taxable income, apply the bracket rates to that figure, then subtract any credits. Tax is charged in slices, so only the income within each bracket is taxed at that bracket’s rate.

What is the difference between a deduction and a credit? A deduction reduces the income you are taxed on, so it is worth your marginal rate. A credit reduces the tax itself, dollar for dollar, up to the amount you can use. When fully usable, a $1,000 credit is generally worth more than a $1,000 deduction, since a deduction returns only your marginal rate. A nonrefundable credit you cannot fully use is capped by the tax you owe and can be worth less.

Is all income taxed at the same rate? No. Ordinary income uses the 10% to 37% schedule, while most long-term capital gains and qualified dividends use a separate 0%, 15%, and 20% schedule, with higher rates for a few categories such as collectibles. Some income, including qualified Roth withdrawals and most municipal bond interest, is not federally taxed at all.

Do I pay income tax on retirement withdrawals? Distributions from traditional pre-tax accounts are generally taxed at ordinary rates, though without payroll tax. Exceptions exist where the account holds after-tax basis or the money leaves as a qualified charitable distribution or a rollover. Qualified Roth withdrawals are tax-free. Social Security is partly taxable depending on your total income for the year.