Federal income tax withholding
IRS Publication 15-T (2026)
Federal Income Tax Withholding Methods, including 2026 percentage method tables for automated payroll systems.
Social Security and Medicare
IRS Publication 15 (2026)
Employer guidance for federal payroll tax, including 2026 employee and employer FICA rates, the Social Security wage base, and Additional Medicare withholding.
Social Security Administration wage base
The SSA contribution and benefit base determination documents the $184,500 Social Security wage base for 2026.
Overtime and the regular rate
U.S. Department of Labor Fact Sheet #56A
Federal guidance on the regular rate of pay under the Fair Labor Standards Act and the general time-and-a-half requirement for covered nonexempt employees.
How we use sources
Primary sources establish calculator constants and calculation concepts. NetPayKit summarizes them for a general audience but does not reproduce all agency instructions or cover every exception. Agency guidance controls if a summary conflicts with an official source.