Practical buffer and risk rules when your tax deductions shrink

Losing some tax deductions – from negative gearing reforms or rule tweaks – means you need bigger buffers, lower risk settings and tighter cashflow rules, not a more aggressive strategy. The core move is to rebuild your safety margin: lift cash buffers, nudge LVRs down over time, and make sure every property stacks up on pre‑tax cashflow, not tax refunds.

Here’s a simple one‑week reset you can actually do.

Turning tax rule changes into clear buffer and risk numbers at the kitchen table.

Step 1: Quantify what you’re really losing

Start by turning abstract policy changes into a dollar number.

1. Estimate the annual tax deduction you’ll lose per property (or business loan).
2. Translate that into after‑tax cashflow: deduction lost × your marginal tax rate.
3. Layer in a 2–3% interest rate rise to see the combined hit.

As a worked example, say a geared investment was generating a $15,000 annual rental loss that you used to fully offset your wage income.

• You’re on a 39% marginal rate (including Medicare).
• Old world: $15,000 × 39% ≈ $5,850 tax back.
• New world (post‑reforms on an established property bought after 12 May 2026): most of that loss may be quarantined, so assume $0 tax back for safety.

Your after‑tax position just worsened by about $112 per week.

To see this in context, pair this article with the worked examples in [/insights/worked-after-tax-cashflow-examples-geared-property-before-after-rule-changes].

Quick rule

If a change pushes your total property cashflow (after tax) beyond what you could cover for 6–12 months from savings and income cuts, your risk settings are too loose.

Step 2: Reset buffer targets for the new world

Earlier guidance suggested 3–6 months of stressed costs for most people, and 6–12 months for highly geared or self‑employed borrowers. With post‑2026–27 tax reforms, think of those as bare minimums, not aspirational goals.

Stressed costs should include:

• All home + investment repayments, tested at least 3% above today’s rate (in line with APRA’s serviceability buffer).
• Essential living costs (realistic, not fantasy-budget).
• Known extras: school fees, insurance, strata and land tax.

For many mum‑and‑dad investors now losing some negative gearing benefits, a practical buffer rule is:

• PAYG households, moderate gearing: 6 months of stressed costs in offset.
• Self‑employed / high gearing: 9–12 months of stressed costs in offset.

If you’re gearing into higher‑priced markets, the 6–12 month guidance from our Eastern Suburbs work still applies, but with more urgency now that tax isn’t smoothing the bumps.