US methodology (tax year 2026)

Model

We show the annual-liability view: 2026 brackets plus the standard deduction ($16,100 single / $32,200 married filing jointly), per IRS Rev. Proc. 2025-32. This is what you actually owe for the year. Per-paycheck W-4 withholding (IRS Pub 15-T Worksheet 1A) differs by design and reconciles at filing; we label every page accordingly rather than mixing the two models as many sites do.

Federal income tax 2026

Seven brackets, 10% to 37%: single thresholds $12,400 / $50,400 / $105,700 / $201,775 / $256,225 / $640,600; married filing jointly at double except the top ($768,700). Head of household is modelled (SD $24,150; brackets per Rev. Proc. 2025-32; state calculations use each state's single schedule, as state HoH tables vary). The four OBBBA deductions are modelled as calculator inputs for 2026: qualified tips (up to $25,000 per return, phased $100 per $1,000 of income over $150,000 single / $300,000 joint), overtime premium (up to $12,500 / $25,000 joint, same phase-out), new US-assembled car-loan interest (up to $10,000, phased $200 per $1,000 over $100,000 / $200,000) and the $6,000 senior deduction (reduced 6% of income over $75,000 / $150,000), plus the regular 65+ additional standard deduction ($2,050 unmarried, $1,650 per married person). All are below-AGI, federal-only, and leave FICA and state tax untouched, per P.L. 119-21 and Schedule 1-A.

FICA 2026

Social Security 6.2% on wages up to $184,500 (max $11,439). Medicare 1.45% uncapped, plus 0.9% Additional Medicare above $200,000 single / $250,000 married (annual-liability thresholds).

401(k)

Traditional contributions reduce federal and (where applicable) state taxable income, never FICA wages; capped at the $24,500 employee limit. Roth, HSA, Section 125 premiums and employer match are not yet modelled.

States: all 50 + DC

No-tax (9, exact): AK, FL, NV, NH, SD, TN, TX, WA, WY. Flat (14, close estimate): 2026 rates on income after 401(k) deferrals (Pennsylvania on gross, as PA taxes deferrals), ignoring their small standard deductions. Graduated (27 + DC, modelled): full 2026 bracket schedules per the Tax Foundation tables cross-checked with state DORs, with each state's standard deduction and personal exemption. State-specific mechanics we model: Alabama's full federal-tax deduction and sliding standard deduction, Oregon's capped federal-tax subtraction with AGI phase-out, Wisconsin's sliding standard deduction, Connecticut's exemption phase-out plus its 2%-rate phase-out (Table C) and three-tier benefit recapture (Table D), New York's tax-benefit recapture per the official IT-2105-I (2026) worksheets (within $1 of the state's own rounding), Vermont's 3%-of-AGI minimum tax, Rhode Island's deduction cliff, Maryland's exemption phase-out, Ohio's $26,050 zero bracket with tiered exemptions, and California's uncapped 1.3% SDI (shown as its own line).

Documented state limitations

Not modelled, and flagged in each result's notes: local income taxes (NYC's 3.078-3.876%, Maryland's mandatory 2.25-3.30% county tax, Ohio municipalities, Yonkers), dependents' exemptions, and most SDI/PFML premiums outside California. Four states (AR, CA, ND, VT) apply 2026 rates on 2025 bracket widths until their indexing is published.

Sources and verification

IRS Rev. Proc. 2025-32 and Pub 15-T (2026); SSA 2026 wage base; Tax Foundation 2026 state rate tables. The engine is covered by automated tests with hand-derived fixtures, including the Social Security cap, Additional Medicare and 401(k)/FICA interaction. Cross-check tool: the IRS Tax Withholding Estimator.