Tax estimate calculator

Tax year 2026. Federal plus California or New York: ordinary and capital-gains brackets, qualified dividends, the Additional Medicare tax, AMT, itemized-vs-standard, the safe-harbor test, the underpayment penalty, and the per-paycheck fix. This is the app's own tax engine compiled to WebAssembly and run in your browser: nothing you type leaves this tab.

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About you

Filing status State Dependents Boxes checked for age 65+ (0–2) Boxes checked for blindness (0–2)

Income for the year

Wages (W-2 box 1, after 401(k) and other pre-tax deductions) RSU vests and bonuses (included in box 1 — enter here as well) Taxable interest Ordinary dividends (1099-DIV box 1a) of which qualified (box 1b) Net short-term capital gain (negative for a loss) Net long-term capital gain (negative for a loss) Self-employment net profit Taxable retirement distributions

Itemized deductions (leave empty to take the standard deduction)

State and local taxes paid (income + property; the cap applies) Mortgage interest Charitable gifts Medical expenses (the AGI floor applies) Other itemized

Equity compensation and AMT

ISO exercise bargain element this year

Paid so far

Federal income tax withheld (projected for the full year) State income tax withheld (projected for the full year) Medicare tax withheld (W-2 box 6) Estimated payments made Paychecks left this year (for the per-paycheck fix; 0 if unknown)

Safe harbor from last year's return (optional)

Last year's total federal tax (Form 1040 line 24) Last year's adjusted gross income

What this is

The same engine the app runs, compiled to WebAssembly. Every line in "how it was computed" is a rule the engine applied, and every assumption it lists is one it makes for the app too. New York City and Yonkers taxes are not modeled; neither are credits beyond the ones the engine derives, foreign income, or part-year residency, which the app handles from your actual records.

The app does the rest: paystub and broker imports, actual vest timing, dated Form 2210 / FTB 5805 penalty math, what-if scenarios, and the W-4 and DE-4 per-paycheck numbers with your real cadence. On your computer; we never see it.

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