About & methodology
Every number on PaycheckNew comes from a published government schedule and is recomputed by a test suite before the site is allowed to build. This page says where each figure comes from, how it is checked, and what the tool deliberately will not tell you.
Who maintains it
PaycheckNew is built and maintained by Hadi, developer and maintainer, and the code is public at github.com/Itsxhadi.
Deliberately not a tax credential. Nobody here is a CPA, and claiming otherwise on a page about money would be the worst thing on the site. What stands behind the figures instead is the citation under every one of them and the test suite below, both of which you can check yourself.
Where the federal numbers come from
Brackets, the standard deduction, the child tax credit and the supplemental withholding rate come from the IRS revenue procedure for each tax year; the Social Security wage base from the Social Security Administration. Read cell by cell from the source documents, not from a summary. Last checked .
Where the state numbers come from
Each state's own department of revenue, linked at the foot of that state's page. All 51 have been checked against the department's published schedule. Where a department prints a running total beside its brackets, the test suite reproduces that exact figure, because that identity only holds if every threshold below it is right, which makes it a checksum over the whole schedule rather than a spot check. That method found eight wrong tables.
Federal figures are 2026; state figures are 2025, because the IRS publishes a year ahead and states publish with that year's return. Where a state withdraws a deduction or credit as income rises and that withdrawal is not modelled, that state's page says so. Anything ever found wrong is listed with before-and-after figures on the corrections page.
How the maths is checked
One command, npm test, runs before every deploy. If any assertion fails the site does not build.
Every bracket table ascends and each federal year has exactly seven bands.
The married standard deduction is double the single one in every year in the table.
No-tax states return zero income tax but still charge their payroll premiums, which is a bug this check caught in Washington.
Social Security stops at the wage base and the additional Medicare tax starts at $200,000.
A 401(k) reduces income tax but not FICA and a section 125 premium reduces both.
The child tax credit phases out at the statutory threshold and never touches a state figure.
Hand-worked figures are reproduced exactly for Texas, Illinois, California and every state whose department prints a running total beside its brackets.
What this tool does not do
- It is not your employer's withholding
- It spreads the annual liability evenly across pay periods. Your employer follows your W-4 and IRS Publication 15-T, and the two are reconciled on your return. The bonus calculator shows both numbers side by side, because for a bonus the gap is large and predictable.
- It does not itemise
- The standard deduction is always applied, federally and at state level.
- Most credits are absent
- The federal child tax credit and the credit for other dependents are modelled. The earned income credit, education and dependent-care credits and every state-level credit are not, and neither is the extra deduction for age 65 and over.
- Local tax only if you enter it
- Except Maryland, where a typical county rate is pre-filled and the result says so.
- Wages only
- No self-employment income, no capital gains, no income taxed on a schedule this engine does not implement.
- It is not tax advice
- For your own circumstances, talk to a CPA or an enrolled agent. The disclaimer sets this out in full.
Found something wrong?
If a figure for your state looks wrong, say so with a link to the official source. It gets checked against that source, fixed in the table rather than on the page, and logged on the corrections page with the date and the before-and-after figures. State tables are moving quickly at the moment, with several states phasing in rate cuts, so this is a real request rather than a polite one.
Hadi · Developer and maintainer
Federal tables checked against the IRS 2026 inflation adjustments on . State figures, where quoted, are each state's latest published schedule, 2025; federal figures are 2026.