Tax & payroll data sources
Primary official references we cite in guides and use when maintaining calculation tables. Always verify current-year publications on the issuing agency’s site.
Federal
- Internal Revenue Service (IRS)
- IRS Publication 15 (Circular E), Employer’s Tax Guide
- IRS Publication 15-T, Federal Income Tax Withholding Methods
- Form W-4, Employee’s Withholding Certificate
- Form W-2, Wage and Tax Statement
- Form 1099-NEC
- Social Security Administration (SSA)
- SSA contribution and benefit base (wage base)
- U.S. Department of Labor, Wage and Hour Division
State & local
State income-tax withholding methods, minimum wage, overtime, and pay-stub rules come from each state’s revenue department and labor department (or equivalent). Our state payroll guides link to the relevant agencies for that jurisdiction.
Starting points:
- Federation of Tax Administrators (directory of state tax agencies)
- DOL state labor office contacts
How we use these sources
Calculation tables follow the methods described in our methodology. Educational pages summarize and cite; they do not replace the official publication. If an agency updates a rate mid-year, we prioritize engine updates and then refresh related guides.