Method
How we verify the tax numbers
Every pay stub generator promises accurate withholding. Ours can be checked against the documents behind it: every rate is published by the IRS or a state revenue department, the link sits beside the number, and a test reproduces the department's own arithmetic. Below is how far that reaches and where it stops.
What is checked today
Federal withholding uses the 2026 tables from IRS Publication 15-T. Social Security and Medicare use the published contribution base and rates. The states are kept one at a time, each with a link to the revenue department guide it came from. Before we mark one verified, a test has to reproduce a calculation the department published, and 52 of 54 clear that bar today.
Income tax is not the whole deduction column. 21 employee-paid programs in 16 states come out of the same paycheck: state disability insurance, paid family and medical leave, smaller funds like Washington's long-term care premium. Each carries its own rate, its own wage cap and its own definition of what counts as wages, which is why they are the lines a generator is most likely to drop.
What “verified” means here
A state is verified when a test reproduces a calculation the state itself published, and not before. Four kinds of published calculation qualify, and each one proves something the others do not.
Kind 1
A control example from the state guide
This is the strongest evidence a department can give us: it has worked one case from gross wage to withheld amount and printed the answer. Reproducing it confirms the order of operations, the rounding rule and every constant in one go.
Kind 2
The state's own calculator
Used where a department publishes a formula but never a worked case. The test records that the answer came from a calculator rather than a printed guide, because a calculator can change at the same address with no revision number to warn anyone.
Kind 3
A closed list of rates from the form
Used where a state has no formula at all and withholding is a single multiplication. Arizona works this way: the employee picks a percentage on Form A-4 and it applies to gross wages. The list is the whole rule, so there is no sequence to get wrong.
Kind 4
A printed withholding table, in at least two cells
A wage bracket table is the department running its own formula for us, so it confirms the sequence much as a worked example does. We take two cells rather than one: a single cell can agree by accident when a wrong deduction is swallowed by the width of a bracket, and two cells from different rows and columns catch that.
Copying the constants of a formula out of the guide and into a test counts as none of the four. It catches a mistyped rate, and a mistake in the order of operations goes straight through it. Where a state offers nothing we can reproduce, it stays unverified and the page says so.
What we could not check
Each state below publishes no calculation for anyone to check against. That is a property of the state rather than work we have not got to yet: we read the rates out of the guide, link the guide, and stop there. The note under each name is the one recorded with the data itself, so you can see what is missing instead of taking our word for it.
Colorado
DR 1098 (10/21/25) states the four steps and nothing else: the department publishes no worked example, no wage bracket table, and the electronic version it calls the DR 1098 Withholding Calculator is that same worksheet in a spreadsheet, with the allowance typed in by hand rather than computed. With nothing of Colorado's own to check a computation against, the entry stays unverified.
District of Columbia
Brackets are the current 2026 ones from the D-40ES booklet. The District has published no withholding booklet since FR-230 Rev. 11/17: OTR Tax Notice 2022-08 says the TCJA impaired the District's ability to produce withholding tables and directs employers to the current rate schedule and the federal allowance amount, which IRS Publication 15-T (2026) sets at $4,300 per allowance. That is the allowance used here. With no worked example, table or calculator of the District's own to check a computation against, the entry stays unverified.
Check one for yourself
Take someone single, paid $4,000.00 a month, with the Step 2 box on the W-4 left unchecked. Their federal withholding is four lines of Worksheet 1A, and following it in the publication takes about a minute.
The steps come from the same table the generator withholds from, and the last line is the figure the generator returns for that employee. When the 2027 tables arrive, the example moves with them.
IRS Publication 15-T (2026) →$4,000.00 × 12 pay periods
$48,000.00
less the $8,600.00 of line 1g, the adjusted annual wage
$39,400.00
in the $19,900.00 row: $1,240.00 plus 12% of the excess
$3,580.00 a year
divided by 12 periods, the figure printed on the stub
$298.33
Why a number you cannot check is worth so little
In September 2026 we compared our federal line with another generator's at three different wages. We could reproduce their figure to the cent at all three, using the rates of last year's annual tax return applied after a deduction that appears in no publication we could find. Withholding is not computed that way, and the year was wrong as well.
The wrong number looked exactly as plausible as the right one. It sat on a tidy document, in the same place, with the same two decimals, and nothing on the page said which year's tables produced it, which method, or what filing status it assumed. Anyone handing that stub to a lender or an accountant has no way to find out.
What keeps it from going stale
When a rate moves, the change has to be looked at before it can ship. Any edit to a figure in the tables stops the release on its own, and it stays stopped until someone has compared the size of the shift with what the update was supposed to do. A state that used to produce a figure and stops producing one sets off the same alarm.
The links are re-checked on a schedule, not once when they were written down. Departments move their PDFs without notice, and a source that has quietly turned into a dead link is no use to you.
What this is not
Nobody outside this project has audited it, there is no certification, and nothing here guarantees that a particular document is right for your situation. We are not tax advisors. This page does not change the disclaimer on the stub or in the terms.
The checking has limits worth naming. Where a state prints its table in whole dollars, the test taken from it allows half a dollar of slack, and slack that wide can hide a small enough error in the annual figure underneath. The two safeguards also cover different ground: the alarm catches a number that moved, while only a reproduced calculation catches a mistake in the order of operations. That is why a state with nothing to reproduce stays unverified instead of being counted as checked.
The tables themselves are open
Everything described on this page is published: the withholding tables for all 51 jurisdictions with a link to the department document behind every line, the control examples that make a line count as verified, and the log of the monthly re-reading of those documents. The repository mirrors what the generator computes with, so it cannot drift into a tidied-up copy kept for show.
The data is under CC BY 4.0. Take it, check it against the same departments we did, or use it in your own work. A validator ships with it that needs nothing installed.
US payroll tax tables on GitHub →Every state page carries the same links and notes for its own rules, and each stub the generator makes says which year's tables produced it.