Methodology

Tax year

Current engine parameters: 2026 (IRS Rev. Proc. 2025-32; SSA wage base 2026).

Federal income tax

Taxable income ≈ gross − employee pre-tax deferrals − standard deduction. Progressive ordinary rates applied. No credits, AMT, or itemizing in v0.

FICA

Employee Social Security 6.2% up to wage base; Medicare 1.45%; Additional Medicare 0.9% above filing-status threshold.

State income tax

v0 supports only states with no broad wage income tax. Other states are rejected rather than guessed.

Housing

Rents come from HUD Fair Market Rent county-level Excel (FY index). FMR is a program benchmark, not Zillow asking rent.

Quality control

Python unit tests with hand-calculated golden cases are the release gate. Browser JS is a convenience mirror.