The whole federal return. Not a bracket lookup.

AGI, then deductions (standard, or itemized: SALT with its cap and phase-down, mortgage interest under the acquisition-debt cap for the loan's origination year, charitable, medical, casualty), then ordinary brackets, then preferential-rate stacking for long-term gains and qualified dividends, then NIIT, Additional Medicare, and AMT. Every component comes back — marginal rate, effective rate, and each line. All five filing statuses. Payroll taxes are modeled too: Social Security 6.2% on the wage base, Medicare 1.45%, and the 0.9% Additional Medicare Tax, alongside the 3.8% Net Investment Income Tax on investment income.

Federal ordinary and capital-gains brackets cover the current tax year and the two before it. The rest of the return — AMT, deductions, equity compensation, Roth conversion analysis — and every state table are built for the current tax year. Projections that run past the last legislated year hold that year's law fixed in real terms; they do not predict future legislation.

Form 6251 with the 26%/28% tiers, the phased-out exemption, and the Form 8801 credit carryforward. Long-term capital gains are folded into the AMT base at ordinary rates rather than keeping their preferential treatment (Form 6251 Part III), so in years with large long-term gains the AMT figure is an upper bound.

ISO exercises (the bargain element as an AMT preference when exercised and held, ordinary income on a disqualifying disposition), NQSO exercises, and RSU vests (FICA-subject supplemental W-2 income) are modeled explicitly.

Roth conversion analysis for a single year: the marginal cost of the converted slice, federal plus state and local, filling to a target bracket, the resulting RMD reduction, and a convert-now vs leave-in break-even that accounts for the early-withdrawal penalty. Also safe-harbor and underpayment estimation with suggested quarterly payments, and withdrawal tax by account type.

SECURE 2.0 start ages by birth year, the Uniform Lifetime, Joint and Last Survivor, and single-life tables, multi-IRA aggregation, the shortfall penalty, and multi-year projected RMD schedules. The joint table applies when the owner's sole beneficiary is a spouse more than ten years younger, and it takes both ages.

Resident returns on each state's own schedule — graduated, flat, or none — with the retirement exclusions (Social Security, pension, IRA) each state actually applies, every rate cited to the state's own revenue department with the date it was verified. Nine states levy no broad income tax. Local layers are modeled where they bite: New York City and Yonkers, every Maryland county, Philadelphia, Detroit, the four major Ohio cities, St. Louis, Kansas City, Louisville, Birmingham, and Wilmington — the earned-income-only ones correctly leave a retiree's IRA withdrawal untaxed. An unlisted Ohio municipality comes back as an explicit unsupported result rather than a silent zero.