Who we are
NetPay Atlas is a small independent team building clear, fast paycheck tools. We're not a payroll company and we don't sell your data — the calculators run entirely in your browser.
Federal income tax
We use the percentage method for automated payroll systems from IRS Publication 15-T (2026), Worksheet 1A, for Forms W-4 from 2020 or later. Wages are annualized, Step 4(a) income is added, Step 4(b) deductions and the Worksheet adjustment ($12,900 married filing jointly, $8,600 otherwise, $0 when Step 2 is checked) are subtracted, the annual table is applied, and the result is divided by pay periods before Step 3 credits and Step 4(c) extra withholding.
Social Security and Medicare
Social Security is 6.2% of wages up to the 2026 wage base of $184,500. Medicare is 1.45% of all wages plus 0.9% withheld on wages above $200,000. Per-paycheck figures show a typical paycheck early in the year; annual totals respect the wage base, and the calculator tells you which paycheck the Social Security cap is reached.
California
California income tax uses the EDD's Method B — Exact Calculation with the 2026 per-period tables: low-income exemption, estimated-deduction allowances, standard deduction, tax-rate table and exemption-allowance credit. SDI is 1.3% of all wages with no ceiling. HSA contributions are treated as California taxable wages; traditional 401(k) deferrals and Section 125 premiums are not.
Other states
- Texas, Florida, Nevada: no state income tax on wages.
- Washington: WA Cares premium 0.58% of all wages and the employee share (71.43%) of the 1.13% Paid Family & Medical Leave premium, capped at the Social Security wage base.
- Illinois: 4.95% after $2,925 per IL-W-4 basic allowance and $1,000 per additional allowance (IL-700-T formula).
How we test
Our test suite reproduces the IRS Publication 15-T wage-bracket tables (60 values across pay frequencies, filing statuses and the Step 2 checkbox), all six EDD Method B worked examples, the Illinois IL-700-T formula and Social Security wage-base checks. A release can't ship if any of them fails.
What we don't cover (yet)
- Pre-2020 Forms W-4 with allowances.
- Year-to-date wages from a previous employer.
- Local taxes in states we haven't launched (for example New York City or Ohio cities).
Sources
- IRS Publication 15-T (2026), Federal Income Tax Withholding Methods
- IRS — 2026 tax year inflation adjustments
- SSA — 2026 Social Security wage base
- California EDD — 2026 PIT withholding schedules (Method B)
- California EDD — 2026 SDI rate
- California FTB — tax rate schedules
- California DIR — overtime rules
- WA Cares Fund — premium
- Washington Paid Leave — premium rates
- Illinois DOR — withholding (Booklet IL-700-T)
Tax data last updated 2026-10-08. Results are estimates, not tax, legal or financial advice. See our terms.