Why the RBA’s cash rate decides what you can borrow
Every few weeks, a small committee in Sydney sets one number, and that number quietly reorganises what almost every Australian household can afford. It is called the cash rate — the interest rate the Reserve Bank of Australia (RBA) charges on overnight loans between banks — and although nobody outside the banking system ever borrows at it directly, nearly every other interest rate in the country is built on top of it. When it moves, home loan rates, business loan rates and savings rates move with it, usually within weeks.
The simple version
Think of the cash rate as the wholesale price of money. Banks buy money at roughly that price and sell it to households as mortgages at a higher price. As at the June 2026 quarter — the most recent certified reading — the wholesale price was 4.35%, and the average price banks were charging home borrowers was about 8.77%. The gap between the two — around four and a half percentage points — pays for the bank’s costs, its capital requirements and its profit, and it has stayed remarkably steady for years. So when you hear “the RBA moved rates”, the practical translation is: the starting point for your mortgage rate just moved, and the bank’s margin will ride on top of it as usual.
Why this decides what you can borrow
Here is the part that matters for property. When you apply for a home loan, the bank works backwards from your income: after your living costs and other commitments, how large a repayment can you sustain? The repayment depends on the interest rate — so when rates rise, the same income supports a smaller loan, and when rates fall, it supports a larger one. Because almost everyone buys property with borrowed money, the cash rate effectively sets a ceiling on what buyers as a whole can pay. It is not one buyer’s problem or advantage; it moves the entire market’s purchasing power at the same time, in the same direction.
There is a second layer many people don’t know about. The banking regulator, APRA, requires banks to test whether you could still afford the loan if your interest rate were 3 percentage points higher than the one you’re offered. At June 2026 rates, that means being assessed as though you were paying around 11.8%. And since February 2026 there is a further rule limiting how much lending banks can write to borrowers taking on very large debts relative to their income. Together, these rules mean the amount you can borrow is decided by the RBA’s rate, the bank’s margin, and the regulator’s safety rules — all three, not just the headline number on the news.
What has actually happened lately
Over the past eighteen months, Australia went most of the way around a complete round trip. During 2025 the RBA cut the cash rate twice, from 4.35% down to 3.60% — borrowing got a little cheaper. Then, between February and May 2026, it reversed course and lifted the rate back to 4.35%, mostly because inflation in housing costs refused to settle. Mortgage rates followed: down to about 8.02%, back up to about 8.77% by June — completing the round trip back to where it started, except that the new lending rules arrived along the way. On 30 September 2026 the RBA went a step further and raised the cash rate to 4.60%.
How APN measures this
Interest Rates (21210) is the part of the APN Codex that tracks the cost of borrowing. Rather than reporting each announcement as news, it compares certified conditions against fifteen years of history — sixty quarterly readings — and asks a single question: are borrowing conditions normal, cheap, or expensive by the standards of the past decade and a half? The certified answer, as at the June 2026 quarter: expensive. Certified settings sit well above the fifteen-year average — not at the record peaks of 2023, but firmly in restrictive territory, and financial markets are pricing them to stay there rather than fall quickly.
What this means for you
If you’re looking to buy: your borrowing capacity is being set at a historically restrictive level, and it is unlikely to expand quickly. Getting a clear read on what you can actually borrow — including the 3% test buffer — matters more than watching for the next announcement.
If you already have a mortgage: the 2025 rate cuts have been substantially unwound. Budgeting on the assumption that current repayments persist is the prudent setting; markets are not pricing near-term relief.
If you’re selling: every potential buyer’s ceiling is set by the same restrictive conditions. Prices are being negotiated inside a borrowing envelope the RBA and APRA control, not one that optimism can expand.
Why your fixed rate can move when the RBA doesn’t
There’s a second borrowing cost in Australia that most people never hear about until it affects them: the price banks pay to lock in money for a fixed term. A variable-rate loan tracks the RBA’s cash rate directly. A fixed-rate loan doesn’t — the bank has to go out and borrow that money for the length of the fix, from investors in the bond market, before it can lend it to you. If those investors are demanding a higher return on their money that week, your fixed-rate quote goes up, even if the RBA hasn’t touched anything. In early September 2026, exactly this happened: government borrowing costs around the world — in Australia, the US, Japan and Germany — rose to their highest levels in well over a decade, largely because governments are borrowing more to fund everything from defence spending to the infrastructure boom around AI data centres. Australia’s own certified interest-rate data already shows the early stage of this: as at the March 2026 quarter, the bond-market vector that feeds this node was running noticeably hotter than the cash rate itself — the market was pricing in more persistence than the RBA had actually delivered. By June the gap had narrowed, as the RBA raised rates in May and bond yields eased. If you’re comparing a fixed-rate offer today with what a friend was quoted six months ago, you’re not being sold a worse deal — you’re seeing a different, and currently more expensive, market.
