Methodology & Tax Sources

Calculation approach

Federal withholding follows the annualized Percentage Method in IRS Publication 15-T for an automated payroll system. The default assumes a Form W-4 from 2020 or later, Step 2 unchecked, no Step 3 credits, and no Step 4 income or deduction adjustment. The calculator subtracts entered pre-tax amounts, calculates annual withholding, FICA, state withholding and supported employee payroll premiums, then divides annual totals by pay frequency.

State coverage

Texas, California, Florida, New York, New Jersey, Illinois, Pennsylvania, and Washington have dedicated 2026 calculation rules. Other location pages remain planning references and are excluded from search indexing until a source-backed engine is completed. Local income taxes are not included unless a page explicitly says otherwise.

Official sources

Review process

Calculation constants are transcribed from government publications and checked against worked examples or published rate descriptions. Changes are reviewed for filing status, annualization, wage caps, allowance treatment, and whether a charge belongs under income tax or a separate payroll program. Pages identify assumptions that the compact interface cannot capture.

Known limitations

This is an educational estimate, not payroll software, tax preparation, or legal advice. It does not fully model W-4 Step 2, dependent credits, multiple jobs, nonresident reciprocity, local taxes, employer-paid premiums, special exemptions, tips, qualified overtime deductions, garnishments, year-to-date wage history, or every benefit’s FICA treatment. New Jersey uses the published graduated rate schedule as a planning estimate rather than reproducing every NJ-W4 rate-selection path.

Update history

July 23, 2026: Replaced the generic state-rate approximation with eight source-backed state engines; changed federal calculations to IRS Publication 15-T; separated Washington and California employee payroll premiums; added national salary, biweekly, hourly, and paycheck-tax tools.

Editorial responsibility

Paycheck Atlas independently maintains the calculation logic and explanatory content. Questions or suspected discrepancies can be sent to dev@evetrend.com. Include the page, inputs, expected result, and official source when reporting a calculation issue. Reports are reviewed before calculation constants are changed.