About

How these numbers are made.

Tax calculators are easy to build and easy to get wrong. This page explains the source trail, arithmetic, and coverage boundaries so you can check the work instead of treating an estimate as a filed return.

Where the rates come from

Federal tax parameters are read from the linked IRS revenue procedures, notices, forms, instructions, and Social Security Administration releases. Commercial fee inputs come from each provider’s public US pricing page.

The state calculator uses a separate, tax-year-specific schedule library. Its source trail distinguishes a dated nationwide compilation used for discovery from the official state-agency directories users must follow for the controlling form and instructions. It is a planning layer, not a representation that every state return rule has been modeled or individually cited on the page.

The 17 calculators keep shared federal parameters in a versioned constants module and state schedules in their own versioned data module. Tests pin the formulas to reviewed examples so a tax-year update cannot silently change an expected result.

• IRS Rev. Proc. 2025-32 — 2026 inflation adjustments — brackets, standard deduction, QBI thresholds
• IRS — 401(k) limit increases to $24,500 for 2026 — retirement contribution limits
• SSA — 2026 COLA announcement — Social Security wage base
• IRS — Schedule SE (Self-Employment Tax) — self-employment tax computation
• IRS — Standard mileage rates — standard mileage rates

Rates were last checked against these documents on 2026-07-25.

How the arithmetic is checked

Each calculator has test cases with expected values worked out by hand, independently of the code. When the code and the hand calculation disagree, one of them is wrong and it gets investigated before anything ships. That process has already caught errors — in the hand calculations as often as in the code.

The tests also run every year end. Because the expected values are pinned to specific 2026 figures, updating to a new tax year deliberately breaks them, which forces a line-by-line review rather than a silent rollover.

Passing tests means the software matches the documented method. It does not mean that the method is professional advice or that every circumstance is modeled. For that reason, each tax-sensitive page also names its exclusions and links to the controlling source.

What these calculators do not do

Being clear about the limits is more useful than pretending there are none.

• State tax is a separate planning layer. The state calculator applies published single and married-joint rate schedules to state taxable income. It does not calculate residency, part-year or nonresident filing, credits, multistate sourcing, or local tax.
• US scope only. The federal tools do not model nonresident-alien or dual-status returns, treaty positions, foreign earned income exclusions or credits, or tax systems outside the United States. The state tool covers the 50 states and Washington, D.C., not US territories.
• The QBI deduction is modeled below the income threshold only. Above it, wage limits and specified-service rules apply. The calculators warn you rather than return a confidently wrong number.
• No credits. Child tax credit, earned income credit, education credits and the rest are not modeled.
• No AMT, no net investment income tax, no capital gains.
• Nothing here is advice. These are arithmetic tools. They cannot see your full situation, and a number produced by a web page is not a substitute for a professional who can.

Privacy, briefly

Every calculation runs in your browser. The numbers you type are never included in a request to our hosting service or saved to a database. The host still receives ordinary web-request data when it delivers a page. See the privacy policy for the full detail on hosting, cookies, and advertising.

Who runs this

Alonso Verdeja, Publisher and product editor. Alonso Verdeja publishes practical calculator websites and documents how every result is produced. He is not presented as a CPA, enrolled agent, attorney, or financial adviser. Federal tax parameters link to IRS or SSA sources; the state planning library publishes its dated source trail and jurisdiction limits.

No professional credential is implied. If a calculator affects a filing, entity election, retirement contribution, or contract decision, verify it with the IRS instructions and a qualified professional. Suspected errors are handled under the editorial and corrections policy.