How taxes actually work.

What counts as income

The starting point is “gross income” — everything you earned in the year, broadly defined. Wages from a W-2 job. Self-employment income. Interest from savings. Dividends from investments. Rental income. Even some forgiveness of debt. The IRS’s position is that unless a specific provision exempts a kind of income, it’s taxable.

A small set of things are explicitly excluded: most gifts, most inheritances, qualified scholarships, some Roth IRA distributions, life-insurance payouts to a beneficiary. These get their own treatment elsewhere.

How brackets work

This is the place most people get lost, so it’s worth saying carefully: tax brackets are progressive, which means each bracket applies only to the income within that bracket. Not to your whole income.

If a single filer in tax year 2026 earns $60,000, the math runs through the IRS’s inflation-adjusted brackets like this:

Total tax is $7,912, or about 13.2% of income. That’s the effective rate — the share of income that ends up paid in tax. The 22% number, the marginal rate, applies only to the last dollar earned. Confusing the two is the source of the persistent “earning more will push me into a higher bracket and cost me money” misconception. It won’t. Each new dollar gets taxed at the bracket it falls into; nothing already earned is reclassified.

Withholding and the W-4

If you have a W-2 job, your employer is required to withhold federal income tax from each paycheck and send it to the IRS on your behalf. The amount comes from a formula based on the W-4 form you fill out when you’re hired. The system is designed to estimate your full-year tax bill and spread it across pay periods.

The W-4 has gotten more honest over time: it now asks roughly the questions the IRS actually uses (filing status, second jobs, dependents, expected deductions) instead of the old “allowance number” abstraction that confused everyone. If your withholding is wrong all year, you either owe a balance in April or get a refund — the topic of the last section.

There are two other federal withholding lines on every paycheck — Social Security (6.2% on the first $184,500 of wages — the 2026 wage base, announced by SSA on October 24, 2025) and Medicare (1.45% on all wages, plus an additional 0.9% on wages above $200,000 single / $250,000 married filing jointly — a statutory threshold not indexed for inflation). Together these are called FICA. They’re separate from federal income tax, fund specific programs, and don’t reconcile on your tax return — what’s withheld is what you pay.

Deductions vs. credits

This is the second place people get lost. Deductions reduce the income that’s subject to tax. Credits reduce the tax bill itself. They are not the same thing, and a credit is almost always more valuable per dollar.

A $1,000 deduction for someone in the 22% bracket reduces their tax by $220. A $1,000 credit reduces their tax by $1,000.

Most filers take the standard deduction — a flat amount based on filing status — rather than itemizing. For tax year 2026 the standard deduction is $16,100 for a single filer and $32,200 for married filing jointly (per IRS Rev. Proc. 2025-32, released October 9, 2025). Itemizing only beats the standard deduction if you have unusually high mortgage interest, state and local taxes, or charitable giving — our piece on standard deduction vs. itemizing walks through the trade-off.

Common credits include the Child Tax Credit, the Earned Income Tax Credit, the American Opportunity (education) credit, and the Saver’s Credit for low- and moderate-income retirement contributions. Some are refundable, meaning they can produce a refund larger than your tax bill; others are not.

What a refund actually is

A refund happens when the total amount withheld from your paychecks during the year, plus any refundable credits, exceeds your final tax bill. You overpaid; the IRS sends back the difference.

The popular framing of a refund as a windfall is mostly wrong. A refund is your own money, returned, after the IRS has held it interest-free for up to a year. There’s a case for a small refund — it’s a forced-savings mechanism for people who would otherwise spend the money — and a case against it for people who could have used the cash flow during the year. Our short piece on this walks through the trade-off.

If you owe more than was withheld, you write a check (or pay online) by the April filing deadline. If you owe a lot — generally more than $1,000 — the IRS may charge a small underpayment penalty for not having withheld enough during the year.

For the practical question of what each line on your paycheck actually is, our walkthrough on how to read a paycheck stub goes line by line, and how to read your W-2 covers the year-end form your employer sends in January. If you also have non-W-2 income — freelancing, savings interest, dividends — our piece on how 1099s work covers the other side.