Architecture
Year-by-year simulation from current age to retirement age. Each year: select career phase → apply wage growth → calculate employer SG → calculate concessional contributions (with carry-forward) → apply 15% contributions tax → apply Div 293 → apply NCCs and bring-forward → apply investment return (interpolated if glide path) → deduct fees → apply Div 296 → grow non-super account.
Contribution timing convention
Contributions are applied before the investment return each year (start-of-year convention). This means contributions earn a full year's return in the year they are made. The mid-year convention — where contributions arrive evenly throughout the year and earn approximately half a year's return — would be marginally more accurate for monthly payroll and quarterly SG cycles, but the difference is small relative to the opening balance and is a common simplification in annual projection models.
Career phases
Multiple phases can be defined, each with a start age, salary, SG rate, and contribution amounts. The engine selects the phase with the highest start age ≤ current age each year. Wage growth is applied from the phase's start age.
Concessional cap
$30,000/yr (2025–26). Employer SG plus personal concessional. If contributions exceed the cap, the excess is counted as NCCs. Maximise concessional option automatically tops up to the cap minus employer SG each year. ⚠ Model limitation: the cap is held at the 2025–26 value for the first year and then projected forward using a fixed long-run AWOTE rate of 3.5% p.a. in $2,500 increments — consistent with RBA and Treasury long-run estimates. This is independent of the user's personal wage growth setting. In practice the cap rises by government decision and may not match this projection in any given year.
Carry-forward
Unused concessional cap from the prior 5 financial years, available when TSB < $500,000. User enters per-year amounts from ATO MyGov. The engine depletes oldest years first (FIFO). Entries older than 5 years at simulation start are discarded.
Contributions tax
15% flat rate on all concessional contributions. Applied before balance update.
Division 293
Additional 15% tax on concessional contributions if income (salary + concessional) exceeds $250,000. User selects whether deducted from super or paid from other income. The $250,000 threshold is legislatively frozen — there is no indexation mechanism — and has been unchanged since 2012. The model treats it as permanently static, which is correct under current law.
Non-concessional cap (NCC)
$120,000/yr (2025–26). Regular NCC and lump-sum contributions share this cap. Bring-forward contributions override this cap in the trigger year. The NCC cap, bring-forward cap ($360k), and all TSB-relative bring-forward thresholds are derived from the projected concessional cap (NCC = 4× CC) and Transfer Balance Cap, and rise with them over the projection using the same fixed AWOTE and CPI rates.
Bring-forward rule
Allows up to 3 years' NCC cap in a single trigger year. Allowable limit gated by TSB at trigger age: full 3-year ($360k) if TSB < $1,760,000; 2-year ($240k) if TSB < $1,880,000; standard 1-year ($120k) if TSB < $2,000,000; $0 if TSB ≥ Transfer Balance Cap ($2,000,000). NCC cap locked to $0 for 1 year (2-year bring-forward) or 2 years (3-year bring-forward) after the trigger.
Downsizer contribution
One-off, exempt from NCC cap. Available from age 55. Capped at $300,000 per person. Applied to super in the trigger year before the investment return step.
Government co-contribution
ATO matches 50c per $1 of NCC up to $500/year. Full $500 if income ≤ $47,488; phases out linearly to zero at $62,488 (2025–26 thresholds, indexed annually). Applied automatically when eligible.
Division 296
Enacted, effective 1 July 2026: tiered additional tax on notional super earnings. Extra 15% on earnings attributable to TSB above $3M (combined 30%); extra 25% on earnings attributable to TSB above $10M (combined 40%). Thresholds CPI-indexed. Marked with disclaimer in the UI.
Investment return
Applied to the post-contribution, pre-fee balance. Flat rate when glide path off; linearly interpolated from start to end rate when on (lerp). Same interpolation applied to MC volatility.
Fund fees
Three components deducted after investment return: (1) investment fee (% of post-return balance); (2) flat annual admin fee ($); (3) insurance premium ($). All default to $0.
Non-super account
Grows at the user's specified post-tax return rate. Same lognormal z-value as super in MC runs (correlated returns). Annual contribution added each year before return.