Methodology and sources
Checked on 2026-10-28. Source: this page lists the primary sources behind every calculator on the site.
Pay Desk builds every calculator from a fact file we maintain ourselves, not from a number copied off another calculator site. This page explains how we build and check those fact files, and lists the primary source behind each figure.
How a figure gets into a fact file
For a federal figure, we read the current IRS publication directly, such as Publication 15 or Publication 15-T, and transcribe the exact rate, threshold, or bracket row rather than summarizing it from memory or a secondary source. For a state figure, we read that state's own labor department, revenue department, or constitution, and we use the federal Department of Labor's state payday table only as an index of which states to check, never as the source we cite on a page, since that table is not updated often enough to cite directly. Every fact file records the figure, the source, and the date we read it.
The withholding engine
Our paycheck and bonus calculators use the Internal Revenue Service's own percentage-method formula from Publication 15-T, Worksheet 1A: your wages are annualized, adjusted for the entries on your Form W-4, matched against the correct bracket row for your filing status, and divided back to your pay period. We did not invent this formula; we transcribed the IRS's own table rows and tested our code against them directly, the same rows an employer's own payroll software uses.
Federal Social Security withholding is 6.2 percent of wages up to the 2026 wage base of $184,500 (IRS Publication 15 (2026), "What's New," page 1 (fetched and read 2026-10-28; 'the social security wage base limit is $184,500'); also ssa.gov/faqs/en/questions/KA-02387.html.). Medicare withholding is 1.45 percent with no wage cap, plus an Additional Medicare Tax of 0.9 percent once wages from one employer pass $200,000 in the year (IRS Publication 15 (2026), page 1 and page 25 (fetched and read 2026-10-28).). Supplemental wages such as bonuses are withheld at a flat 22 percent, rising to 37 percent on the portion of a year's supplemental wages over $1,000,000 (IRS Publication 15 (2026), "What's New" and section 7 (fetched and read 2026-10-28: 'the withholding rate on supplemental wages remains 22% (37% if supplemental wages paid to an employee during the calendar year exceed $1 million)').).
What is not sourced yet
We say so when a figure is not fully sourced rather than guessing at it. For example, our 2026 tax brackets page shows the full Single and Married Filing Jointly schedules from Revenue Procedure 2025-32, but it does not show the middle Head of Household bracket thresholds, because our own search turned up disagreeing secondary sources and we have not yet read the primary IRS document directly for that filing status. We would rather leave a gap visible than publish a guess.
State sources on this site today
| State | Income tax source | Final paycheck source |
|---|---|---|
| Texas | Texas Constitution, Article 8, Section 24-a, "Individual Income Tax Prohibited" (added Nov. 5, 2019 by the voter-approved constitutional amendment, Proposition 4, replacing the repealed Section 24; tlc.texas.gov/docs/legref/TxConst.pdf, read 2026-10-28): "The legislature may not impose a tax on the net incomes of individuals, including an individual's share of partnership and unincorporated association income." | Texas Workforce Commission, 'Final Pay' (efte.twc.texas.gov/final_pay_severance_benefits.html), implementing Texas Labor Code Section 61.014. |
We add a state only once we can cite its own income tax rule, its own local-tax position, its own disability or paid-leave payroll deduction (or confirm it has none), and its own labor department's final-paycheck rule. A state with no page yet simply has not cleared that bar for us.