- Income & dates
- Homes, debts & spending
- Accounts & assumptions
The MoneyWhatIf handbook
Understand your plan.
See what could change.
Learn how your income, spending, saving, and taxes shape your forecast. Start with the basics, find a guide to any page, or explore the calculations behind a number.
Follow one year Start here, then explore at your own pace
- Money coming in
- Tax, bills & debt
- Saving or withdrawals
- Cash & accounts
- Equity & other debt
- Net worth & milestones
Closing balances open the next year
01AnnualEach year settles before the next begins.
02ConsistentEvery chart and detail uses the same calculation.
03Whole-planTax, housing, saving, and spending affect one another.
04Scenario, not promiseResults follow assumptions; they do not predict markets.
Explore the handbook
Find the explanation you need.
Read how the forecast works, get help with a specific page, or look up a financial concept. Each guide explains the result and the assumptions behind it.
01
Projection & graphs
Read every bar, line, balance, display mode, and the exact order used to close one plan year.
Read the chapter 02Tax & plan funding
Follow income through federal, state, local, payroll, gains, required withdrawals, Medicare, and the withdrawal waterfall.
Read the chapter 03Plan pages
Find your way around each page, learn what the controls do, and get practical tips for reading your results.
Read the chapter 04Technical concepts
Look up a financial term, follow a worked example, and see how MoneyWhatIf uses it in your forecast.
Read the chapterThe annual loop
How one year becomes the next
The order matters: taxes change take-home pay, take-home pay limits saving, and spending can create a need for withdrawals. Each step sees what the earlier steps already changed.
- 01Homes
Advance each property
Update values, mortgages, ownership costs, rent, purchases, and sales before building the household ledger for the year.
- 02Cash in
Build income & pre-tax saving
Add active income and rent, take any mandatory pension contribution off the pay, calculate payroll tax on the whole wage, and fit pre-tax account elections to compensation and legal limits.
- 03Tax & saving
Price tax & grow accounts
Add cash interest and dividends; calculate federal, state, and supported local income tax; fit after-tax saving to take-home pay; then apply the year’s return to opening balances and add current contributions, deposits, and employer match.
- 04Cash out
Pay the year’s bills
Subtract housing, everyday spending, life events, standalone debt payments, property-sale tax, Medicare, and its income-related surcharge (IRMAA).
- 05Funding
Fund or allocate the result
Process required minimum distributions (RMDs), any strategy conversion, scheduled distributions, named-account purchases, and required priorities. Then follow the saved account-and-property order for a gap, or the surplus priorities when cash is left.
- 06Result
Close the year
Record cash, account balances, home equity, standalone debt, taxes, modified adjusted gross income (MAGI), and net worth. Closing cash, asset, property, and debt balances open the next year; settled MAGI is retained for Medicare’s later lookback.
One plan, several readings
Your guide to each page
Explore your forecast from different angles. Most pages use the same projection; Strategy Lab tests changes against it. These guides explain what to look for and how to use the controls.
Explore your planRead your forecast, compare strategies, and explore taxes, resilience, and more.
Projection
Explore your forecast, inspect a year, and adjust the assumptions behind it. The Projection page brings your charts, plan settings, income, property, spending, and investments together.
Read the guide →Strategy Lab
Strategy Lab tests possible changes against your current plan, then compares their effects on a goal you choose. Review individual actions or combinations, and try them in What-If before saving.
Read the guide →Goal Plan
Choose what your plan needs to achieve, say which changes you are willing to make, and review a tested path toward that target.
Read the guide →Taxes
See how much tax your plan pays each year and why. Explore tax categories, bracket charts, detailed worksheets, and the estimated tax on an extra dollar of income.
Read the guide →Financial wellness
Review your forecast as a financial scorecard. Each card answers a planning question with a rating, a key figure, and an explanation. Use filters to focus on the areas you want to explore.
Read the guide →Plan resilience
Run your plan through hundreds of reshuffled historical market paths. Compare the range of outcomes, see when money runs short, and open individual runs to understand what happened.
Read the guide →Tax planning
Compare Roth conversion strategies, then explore capital gains harvesting. Review the tax cost today, the effects in later years, and the proposed schedule before applying a strategy to your plan.
Read the guide →Estate
Start with your projected assets and debts, then explore the taxes and costs that could affect your estate. Adjust the estate assumptions to see how much may reach your beneficiaries.
Read the guide →Reports
Preview and download your plan as a PDF summary or CSV tables. Each report uses the projection already on screen, with charts, key figures, and annual details you can review or share.
Read the guide →Set up & manageCreate a plan, keep your finances current, and organize or share your work.
Starting a plan
Build your first forecast with a short survey or a guided walkthrough. Add your household details, income, property, spending, and investments, then refine the plan as you learn.
Read the guide →Household Overview
Review your household’s current figures, follow a metric through saved history, and open the plan you want to explore next.
Read the guide →Default settings
Save a reusable set of starting assumptions for new plans, including the current year’s earlier income and withholding.
Read the guide →Plans, profiles and sharing
Create and compare plans, organize them by profile, and share them for others to view. Learn how copying, importing, and sharing work, including what a viewer can access.
Read the guide →Examples and walkthroughs
Open a public example to explore a complete plan, or replay a page walkthrough from your account’s tour library.
Read the guide →Account & accessManage sign-in security and display preferences.
Account and security
Confirm your email, manage your password and authenticator, choose display preferences, and understand account deletion.
Read the guide →Plain-language glossary
Common financial terms
These are the few labels needed to read the calculation. Each linked term opens a fuller explanation, worked example, and statement of the model’s limits.
RMD
A withdrawal the model requires from an eligible pre-tax retirement account in the plan year the owner reaches the applicable starting age and afterward.
Full explanation →IRMAA
An extra Medicare Part B and Part D charge based on household MAGI from two years earlier.
Full explanation →MAGI
The model’s income measure for rules such as Medicare surcharges, IRA phaseouts, and NIIT; the exact inputs depend on the rule.
Full explanation →Cost basis
The amount treated as already paid for. When an asset is sold, only value above its remaining basis is modeled as gain.
Full explanation →Tax gross-up
Withdrawing more than the cash gap so the amount left after tax and any penalty is enough to pay the bill.
Full explanation →NIIT
A modeled 3.8% federal surtax on certain investment income when MAGI exceeds its fixed threshold.
Full explanation →Today’s money
A view that discounts settled future dollars into beginning-of-plan purchasing power without recalculating tax.
Full explanation →Standalone debt
A separately modeled loan or balance with its own interest and payments. Its remaining balance is subtracted from net worth.
Roth conversion
A modeled transfer from an eligible traditional account into Roth. The converted amount is ordinary income now; afterward it follows the destination account’s modeled Roth and early-access rules.
Full explanation →More words than these? Browse all 289 financial terms →
Core relationships
What the headline numbers mean.
You do not need formulas to use the forecast. These simple relationships just make the main labels easier to understand; account-level tax and timing still happen underneath.
Cash in can include income, rent, interest, sale proceeds, and withdrawals. Cash out can include tax, contributions, housing, spending, debt, Medicare, and surplus allocations.
Value follows the chosen appreciation path. The mortgage balance follows its amortization schedule; rent and ownership costs stay cash flows.
Mortgages are already reflected in home equity. The taxable-net-worth view also estimates the tax embedded in assets if they were sold or withdrawn in that year.
The engine calculates in future dollars first, then discounts the finished result. Switching the chart does not rerun the tax calculation.
Tax treatment
Tax depends on where the money came from.
The model identifies each kind of income, saving, or withdrawal and applies tax at the right point in the plan.
Pre-tax retirement
Contributions reduce ordinary taxable income. The full withdrawal is ordinary income later, with an early-withdrawal charge when the model’s age rule applies.
Roth & cash
Roth contributions come from take-home pay and qualified modeled withdrawals add no tax. Savings interest is ordinary income in the year it is earned.
Brokerage & property
Only growth above cost basis is treated as a gain. Home-sale exclusions and the year’s other income are considered before the sale tax is added.
Wages & benefits
Earned income pays payroll tax. Social Security follows its provisional-income formula, with no more than 85% included in federal taxable income here.
Projection tax, not tax-prep tax. The schedules are intentionally simplified: progressive federal and state brackets with the larger of the standard and itemized federal deductions each year — state and local taxes under the SALT cap, mortgage interest, declared giving and medical — plus the alternative minimum tax beside the regular calculation, selected local income taxes, payroll tax, gains, qualified charitable distributions, the states’ own itemized deductions where a state writes one, and listed state retirement-income exemptions. Most credits and carryforwards, cross-border state or local tax detail, and return-specific exceptions are not.
Data & assumptions
What is yours, what is built in.
A result is only as current as its inputs and its reference rules. The page keeps those two sources distinct.
01Editable
Your plan
Income, timing, state and locality, household ages, homes, standalone debts, expenses, account balances, contributions, return assumptions, and what-if events.
022026 snapshot
Reference rules
Encoded 2026 federal schedules, plus payroll, contribution, Medicare, IRMAA, and RMD rules; supported-state and selected-local schedules are still 2025. Brackets and deductions for ordinary income are carried forward mechanically with plan inflation; separately encoded fixed thresholds stay fixed.
03Optional
Market history
Calendar-year return series from Yahoo Finance, pulled August 16, 2026, and carried back to 1928 from the NYU Stern (Damodaran) annual-returns record. Historical mode walks the selected series year by year; each series states whether it includes reinvested dividends or is price-only.
04Live result
Calculated output
Within a run, charts, milestones, tax rows, and net-worth figures read the same settled annual ledger. Resilience results come from additional full runs of that engine.
Returns & sequence risk
A flat 7% and real market history answer different questions.
Without historical mode, each account uses its configured return for that plan year, whether flat or custom. Historical mode instead applies each available calendar year in order — so a crash near retirement can look very different from the same average return spread smoothly across the plan. It is a stress test of one historical path, not a probability or Monte Carlo forecast. Where the series has no observation, the account falls back to that plan year’s configured return.
Read the result well
Useful for tradeoffs. Not a guarantee.
The result is conditional.
Change inflation, a return, a retirement date, or a spending path and the future changes with it. That sensitivity is the point of a what-if model.
Years are the unit.
The engine models annual cash flow. Dates can control partial income and event timing, but it is not a daily brokerage or month-by-month budgeting system.
Law changes.
Tax and benefit tables are a fixed code snapshot. Check their vintage before using the output for a real decision.
Advice still belongs to people.
The model can make consequences visible. It cannot know your risk tolerance, legal situation, or everything a tax return knows.
Now make it yours