Every assumption, on the table.

The whole household — people, accounts (401(k), IRA, Roth, HSA, 529, taxable, debts, and more), income streams, expenses, goals, and liabilities — is a single plain-JSON state document that you own and can export at any time. Facts live there; the engine reads them.

Every projection echoes the assumptions it used — returns, volatility, inflation, tax year, marginal rates — in the same response as the result. Any number can be traced back to the inputs that produced it, and a follow-up question is one changed parameter away.

Projected numbers are always re-derived from inputs, never served back from a cache. The state document holds facts and scenarios hold hypothetical deltas. Snapshots are the one place computed results are kept — deliberately, as an immutable, dated record of what the plan showed at that moment.

A target amount and date with an importance level (the probability of success you're aiming for), projected as a balance and progress band with a success probability at the target date. Accounts and income streams can be earmarked to a goal.

Tiered, safe-harbor, and QACA match formulas, with cliff and graded vesting schedules.

Full amortization and payoff schedules, for a mortgage and for credit-card, student, auto, and personal loans.

Income and expense modeling and savings-rate analysis, feeding the household surplus into the projection.

Immutable, diffable point-in-time records, so you can track how a plan changes over time.

All 50 states + DC are modeled, but only as full-year resident returns: there is no nonresident or part-year input. Most state credits are not modeled, and Washington's separate capital-gains tax is not either. More detail →

Long-term capital gains are folded into the AMT base at ordinary rates rather than keeping their preferential treatment (Form 6251 Part III). Treat AMT output in years with large long-term gains as an upper bound. More detail →

For plans with ongoing contributions, the closed-form engine's 10th percentile runs roughly 12–24% below Monte Carlo, depending on volatility and horizon. A fix is decided but not shipped; ask for Monte Carlo when the downside band matters. More detail →

When household spending exceeds income, the engine funds the deficit as a proportional drawdown across accounts by balance, and does not tax that drawdown or apply a tax-aware withdrawal order (e.g. taxable before pre-tax before Roth). More detail →

Age-based income and expense rules are not evaluated yet, RMDs are not forced out during the projection, and employer match uses simplified 401(k) limits. Each simplification is stated in the response when it applies. More detail →

The engine models income, payroll, and capital-gains tax during your lifetime. It does not model estate tax, gift tax, the step-up in basis at death, or any wealth-transfer planning.

The engine is built for the current tax year and its published tables. Projections that run past the last legislated year hold that year's law fixed in real terms — they do not predict future legislation. More detail →

Allocation is asset-class only — stocks, bonds, cash, and the handful of categories in the table above. The engine has no model of any individual stock or fund, so it cannot tell you which one will do better, and it will not tell you what to hold. It does do the tax math on positions you already own — capital-gains treatment from cost basis and holding period, so you can see which of two sales costs less in tax. That is a tax calculation, not a judgment about the investment.