Borrowing rules are what separate a family that uses debt to build wealth from one that simply carries risk on a fixed repayment schedule. In mid-2026, with the RBA cash rate sitting at 4.35%, that difference matters more than it has in years.
Most Australian families don’t borrow recklessly. Instead, they borrow the way the bank says they can. However, a lender’s approval tells you what you’re allowed to borrow — not what you can safely hold. That gap is exactly where clear borrowing rules earn their keep.
Consider the current backdrop. In May 2026, the Reserve Bank lifted the cash rate to 4.35% as inflation re-accelerated toward 4.2%. Moreover, the major banks are now genuinely split on the June decision — some tip a pause, others another rise. Put simply, the direction of rates is uncertain, and uncertain is precisely the condition your borrowing should be built to survive.
This is why a defined set of borrowing rules matters so much right now. A loan without rules is just risk with a repayment schedule attached. By contrast, a loan governed by a few non-negotiable rules becomes a tool — one you control, rather than one that quietly controls your household.
“A bank approval tells you what you’re allowed to borrow. It says nothing about what you can safely hold through a full rate cycle.”
The six rules of the Borrower’s Code
None of these rules are about borrowing less for its own sake. Rather, they’re about borrowing in a way that holds up when conditions change. Importantly, treat them as guides, not commandments. In the right circumstances — with the right buffers already in place — some can be stretched or set aside deliberately. The point is to bend a rule by choice, not by accident. Let’s walk through each one.
Borrow with a buffer, never to the edge
The single most common borrowing mistake isn’t borrowing too much in theory. Instead, it’s borrowing right up to the maximum a lender will approve. As a result, there’s no slack left in the system when something moves — and something always moves.
A buffer is simply the gap between what you borrowed and what you could have. Crucially, it also means holding accessible cash — ideally three or more months of repayments — sitting in your offset account, separate from your emergency fund. For more on building that base layer, see our guide on building a rainy-day fund that actually works.
If a rate rise, a repair bill or a quiet quarter at work would leave you scrambling, you’ve borrowed to the edge. A buffer turns those events from emergencies into inconveniences.
Stress-test every loan at +3% before you sign
Australian lenders are required to assess your loan with a serviceability buffer — currently around three percentage points above the actual rate. However, families rarely run that same test on themselves before committing. That’s a mistake worth fixing, because the numbers are sobering.
Take a benchmark dual-income household on $280,000 combined, carrying a $1,000,000 home loan. For example, at a 6.4% variable rate, the repayment runs near $6,250 a month. Test the same loan at 9.4% — the +3% stress level — and it climbs to roughly $8,340 a month. That’s about $2,090 more every month, or close to $25,000 a year.
Before you sign, ask one honest question: could we absorb the +3% repayment without selling an asset, raiding super, or stopping our investing? If the answer is no, the loan is too big — not the rate too high.
Keep repayments under your cash-flow ceiling
In Australia, the old “keep repayments under 30% of income” rule simply doesn’t hold for high earners. A more realistic working ceiling for a strong dual income sits closer to 50–60% of net household income. That said, it’s a guide, not a hard line — and the current rate environment shows why your own numbers matter. On $280,000 combined, a household nets somewhere near $16,500 a month after tax.
At that level, a 50% ceiling lands near $8,250 a month, and 60% near $9,900. Our $1M loan at 6.4% costs about $6,250 — close to 38% of net, comfortably inside the range. Stress-test it at 9.4%, though, and the repayment hits about $8,340 — roughly 50% of net. That’s right at the prudent edge, which is exactly why the buffer and stress-test rules come first.
Remember, the bank already stress-tested you at about +3% to approve the loan. Still, knowing your own ceiling — and where today’s repayment sits against it — is what keeps the decision in your hands, not the lender’s.
Write your exit conditions before you need them
Pilots don’t improvise an emergency landing. Likewise, the families who navigate rate stress best decide their responses in advance — calmly, with a spreadsheet, not in a panic at 11pm. These pre-set triggers are your exit conditions.
For instance, you might agree as a couple: if our buffer drops below three months, we pause discretionary spending. If one income stops for more than six months, we refinance or restructure. Therefore, when the moment arrives, the decision is already made — you’re simply executing a plan.
The worst financial decisions are made under pressure. Written exit conditions move the hard thinking to a calm moment — so the stressful moment only needs action, not analysis.
Give every borrowed dollar a clear job
Not all debt is equal, and treating it as one undifferentiated blob is how families stay stuck. We think in three tiers. First, bad debt — credit cards, BNPL, car loans — which costs you and builds nothing. Next, good debt — a sensible mortgage on an appreciating home. Finally, smart debt — deductible investment debt, used deliberately.
The goal isn’t to avoid borrowing. Rather, it’s to keep climbing that ladder — clearing bad debt, structuring good debt well, and using smart debt with intent. Strategies like turning your mortgage into a quiet wealth engine and using home equity to invest the smart way live on that top rung. Interest on genuine investment borrowings may also be deductible — see the ATO guidance on investment income deductions.
If you can’t say in one sentence what a borrowed dollar is doing for you, it probably isn’t doing much. Every dollar of debt should have a job — and a deadline.
Make sure the loan survives 1.5 incomes
Dual-income borrowing carries a hidden assumption: that both incomes keep flowing, uninterrupted, for thirty years. In reality, parental leave, redundancy, illness and career breaks are normal life events — not rare ones. Consequently, a loan that only works on two full incomes is built on a best-case scenario.
The fix is straightforward. Test the loan at roughly one-and-a-half incomes and see whether it still holds. If it does, you’ve built genuine resilience. If it doesn’t, you now know your real margin of safety — and can size the loan, or the buffer, accordingly.
A loan that works on two incomes is a loan that works when nothing goes wrong. A loan that works on 1.5 is a loan that works in real life.
The stress test in numbers
Here’s the heart of the Borrower’s Code on a single page — the same $1,000,000 loan, viewed through the lens of the rules above.
Why these borrowing rules work
Notice what the borrowing rules above have in common. None of them try to predict where rates go next — a game nobody wins reliably. Instead, they build a structure that holds up whichever way the RBA moves on 16 June and beyond. That’s the whole point: resilience by design, not by forecast.
If your repayments are rising and cash flow feels tight, our guide on keeping cash-flow momentum in a high-inflation environment is a practical next read. Ultimately, the families who borrow with rules are the ones still standing — and still buying — when others are forced to sell.
Start with one rule this week. Run the +3% stress test on your own loan, and check whether your buffer covers the gap. From there, the rest of the code falls into place. Victor explores debt structuring and property finance in more depth on the Elevate Your Wealth podcast, and the principles behind this code run through his book, 7 Basic Wealth Strategies.
Prefer to listen? Catch this episode on the Two Incomes, One Plan podcast.
Victor Idoko — CFA · CFP · M.Com (Finance) — is the founder of CFV Advisory, where he helps Australian dual-income couples turn strong incomes into lasting wealth. He is the author of 7 Basic Wealth Strategies and host of the Elevate Your Wealth podcast.
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This article contains general information only and does not take into account your personal objectives, financial situation or needs. It is not personal financial advice. Repayment figures are illustrative estimates based on the rates and loan size stated and will differ from your circumstances. Interest-rate movements and bank forecasts are uncertain and subject to change. Consider seeking advice from a licensed financial adviser before acting. CFV Advisory operates as an authorised representative under its Australian Financial Services Licence.