Sources & Citations

This page is a directory of official agency reference links used during product and content research. It is not a complete source manifest, and a live link does not by itself establish the effective date, exact implemented method, rounding, reachable inputs, persistence, or official-oracle coverage required for certification.

For a step-by-step walk-through of how these sources are used in the math, see How TakeHome IQ Calculates Your Paycheck.

Federal Authorities

These are live IRS and SSA reference links. They have not been archived as approved federal certification entries in the 2026 jurisdiction corpus, so this directory does not certify federal rates, thresholds, forms, supplemental methods, or exact examples.

• IRS Publication 15-T — Federal Income Tax Withholding Methods
• IRS Publication 15 — Employer’s Tax Guide (Circular E)
• IRS Form W-4 — Employee’s Withholding Certificate
• IRS Form W-4 instructions
• IRS Publication 505 — Tax Withholding and Estimated Tax
• SSA Contribution and Benefit Base (Social Security wage base)

State Tax Authorities and Withholding Guides

The list below contains selected state-agency reference links used by dedicated paycheck pages on this site. It is not a complete 52-jurisdiction certification inventory. Some jurisdictions do not impose an individual income tax on wages. That state-PIT fact does not establish the absence of FICA, another work-state tax, a local tax, or an employee payroll-program line. The links below are scoped to the fact each source actually supports.

Link Review and Certification

The links above are reviewed as reference links. Certification is a separate process: the controlling publication must be archived with retrieval and effective dates, a hash and locator, then tied to the implemented method, reachable inputs, persistence, and exact official examples. State selection in the app is nationwide, but certification status and coverage limits vary by jurisdiction and rule family.

Reference links reviewed: 2026-07-13. This date is not an effective-date or certification assertion.

Spot a broken link, an outdated citation, or a missing source? Email me — corrections land in the next verification pass.