Compound-growth model
The available tool is a pure client-side JavaScript calculation with no dependency on live market data. The starting balance compounds monthly; a contribution is made at the end of each month. The formula for a period is balance = balance × (1 + annualRate/1200) × (1 − annualFee/1200) + contribution.
Future-dollar balances are divided by (1 + inflation/1200)^(months) to show an approximate value in today’s dollars. A lump sum, if entered, is added after compounding at the end of the specified year. Contribution increases apply at the start of a new 12-month period. The model does not perform tax calculations, account-level charges, transaction costs or variable market returns.
The precise regression case is $10,000 initially, $500 at each month end, 20 years, 6% annual nominal return, 0% fees: $264,122.49. The test suite asserts this value and zero-return behaviour rather than only checking a broad range.
Scenario policy
Three return assumptions are shown as low, middle and high mathematical scenarios, not probabilities, market forecasts or target returns. They can be edited. The fee and inflation figures are assumptions supplied by the user, not live official rates. Values can be negative if an assumed rate is negative.
Future Australian rates engine
Income-year and jurisdiction-specific calculators will rely on officially published tables with a source URL, verification date and legal status. The feature must remain disabled if any essential rate, withholding coefficient, threshold or exception is unverified. See official reference sources.
Quality process
Our acceptance process includes test vectors, input boundaries, comparison to relevant official examples, responsive and keyboard checks, and content review. No automated test can replace independent professional verification of legally significant calculations.