Our Sources & Methodology

Federal figures for tax year 2026 come from the following official publications. When a number appears anywhere on this site, it is because one of these documents put it there.

• IRS Revenue Procedure 2025-32 — the IRS's annual inflation adjustments for 2026. This is the source of our federal income tax brackets, the standard deduction ($16,100 single, $32,200 married filing jointly, $24,150 head of household), and the $2,200 Child Tax Credit amount. Read the IRS announcement or the full text of Rev. Proc. 2025-32 (PDF).
• IRS Publication 15-T — Federal Income Tax Withholding Methods. Our federal withholding follows the annualized percentage method in this publication, the same method payroll departments use with Form W-4. Read Publication 15-T.
• IRS Publication 15 (Circular E) — the employer's tax guide behind our supplemental wage rates (22% up to $1 million, 37% above) used in the bonus calculator. Read Publication 15.
• Social Security Administration — the SSA sets the Social Security wage base each year. The 2026 taxable maximum is $184,500, which caps the 6.2% Social Security tax in our engine. See the SSA's Contribution and Benefit Base table.
• One Big Beautiful Bill Act (Public Law 119-21) — the 2025 law that created the temporary deductions for tips, overtime premium pay, car loan interest, and seniors (tax years 2025–2028). See the IRS's One, Big, Beautiful Bill provisions page and the enacted text on Congress.gov.
• Form W-4 — our calculator's inputs mirror the W-4's structure: filing status, multiple jobs, dependents, other income, and extra withholding. About Form W-4.
• Schedule 1-A (Additional Deductions) — the new Form 1040 schedule where the four OBBBA deductions are actually claimed. Our guides reference its parts line by line, following the IRS fact sheet. What to know about Schedule 1-A.

There is no single national table for state withholding — each state publishes its own. Every state calculator on this site is checked against that state's own Department of Revenue or Taxation: its official withholding tables, rate schedules, and standard deduction amounts. Each state page names its source and carries a "Last verified" stamp so you can see when it was last checked against the authority below.

Nine states — Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming — levy no tax on wage income, so their calculators apply federal tax and FICA only. Where a state has a flat tax, we use the statutory rate; where it has graduated brackets, we use the official bracket schedule.

To compare all 51 systems side by side — no-tax, flat, and graduated, with top rates and standard deductions — see our State Income Tax Rates & Brackets 2026 comparison.

Every paycheck estimate runs the same steps, in the same order a payroll system does:

1. Gross pay for the pay period, based on your salary or hourly rate and the pay frequency you select.
2. Pre-tax deductions — traditional 401(k) contributions, HSA contributions, and pre-tax premiums — come out first, reducing the wages that are taxable for federal income tax.
3. Federal income tax withholding using the annualized percentage method from Publication 15-T: wages are annualized, the standard deduction and the Rev. Proc. 2025-32 brackets are applied for your filing status, your W-4 entries for dependents, other income, and extra withholding are factored in, and the result is divided back to your pay period.
4. FICA taxes — Social Security at 6.2% on wages up to the $184,500 wage base, Medicare at 1.45% on all wages, plus the 0.9% Additional Medicare Tax on wages above $200,000 ($250,000 if married filing jointly, $125,000 if married filing separately).
5. State income tax using that state's own rate schedule, standard deduction, and withholding rules from the authorities listed above.
6. Net pay — what is left after any post-tax deductions you enter.

An honest caveat: for graduated-bracket states, the state result is an estimate built on the state's official brackets and standard deduction — it is not a copy of your employer's payroll output. Small differences against a real pay stub are normal: employers may apply wage-bracket tables instead of the percentage method, round differently, or apply a local tax (such as a city tax) that a statewide calculator does not include. Each state page shows its own source and verified date so you can judge how current its figures are.

All federal and state figures live in one data file (tax_data_2026.json) that every calculator on the site reads. There are no hand-typed copies of a tax rate scattered across pages, so a figure can never be updated in one place and go stale in another. When the IRS or a state authority publishes a correction or a new table, we update the data file first, and every calculator picks it up.

Two automated checks guard the result. A daily audit compares the live site against the data file and the official sources and corrects any drift it finds. A separate health check runs every two hours and confirms that every page and data file on the site loads correctly. On top of that, our research desk re-verifies each state page against its tax authority on a rolling basis — that is the "Last verified" date you see on state pages.