Scenario Analysis
Stress test your finances under different conditions
Mortgage Stress Test
How would different interest rates affect your repayments? Stress zone is >30% of net income.
| Rate | Monthly Payment | % of Income | Status |
|---|
PPOR IP% Optimizer
Find the optimal income-producing % for your PPOR based on current interest rate and expected property growth
How The Optimizer Works
For each combination of interest rate and property growth, the optimizer sweeps IP% from 0% to 50% and finds the % that maximises annual net benefit:
At >0% IP (Rental): $300/wk becomes assessable rental income, triggers deductions + partial CGT
annual_tax_refund = (IP% × (interest + holding_costs) − rental_income) × marginal_rate
Offset mode: refunds → offset account (PPOR portion only = (1 − IP%) × loan)
wealth = min(cumulative_refunds, ppor_balance) + cumulative_interest_saved ← risk-free, capped
Market mode: refunds → invested at chosen return %
portfolio_FV = refund × [((1 + return)^years − 1) / return] ← the flywheel
CGT (pre-reform gains): gain × IP% × 50% discount × marginal_rate
CGT (post-1 Jul 2027 gains): gain × IP% × inflation_discount × max(marginal_rate, 30% floor)
net_wealth = flywheel_FV − CGT
Key insight: Higher interest rates favour higher IP% (more deductible interest). Higher property growth favours lower IP% (more CGT exposure). Post-reform CGT is higher — the PPOR exemption is worth more than before. "Never sell" removes CGT entirely — optimal is always 50%.
Tax-Time Checklist
- Set current interest rate (check your lender)
- Estimate growth using comparable sales or CoreLogic
- Find the highlighted cell → that's your optimal IP%
- Claim that % of interest + holding costs for the FY
- Remember: IP% can change each year — re-optimize annually
- IP% must be defensible (actual use — rooms, shared spaces)