The RBA rate hike on 29 September 2026 lifted the cash rate target by 25 basis points to 4.60 per cent, its highest level since 2011. The Reserve Bank said some of the upside risks to inflation it had flagged in August were materialising: global energy prices were well above its August assumptions, AI-related demand was lifting prices for technology goods, and domestic capacity remained under pressure.
The decision was unanimous and the fourth increase of 2026. By the time it arrived, it surprised almost no one. What makes September worth studying is how quickly that expectation formed.
In late August, a September hike was a minority view. Economists polled a month earlier had expected the Reserve Bank to hold, with the cycle topping out at 4.35 per cent. By the final week of September, that view had all but disappeared. In a Reuters poll taken between 17 and 24 September, 33 of 34 economists expected the cash rate to rise to 4.60 per cent. A view that looked settled at the start of the month had been fully reversed before the month was out.
Behind the RBA rate hike: what changed in four weeks
The distance travelled is clearer when set against the previous meeting. Westpac’s chief economist noted that at the 11 August meeting, an extended period on hold had looked like the base case, with the data having turned against the RBA’s more hawkish view.
The Board’s September statement filled in the detail. Beyond energy prices, AI-related demand and capacity pressures, it noted that the Middle East conflict had broadened, that business liaison indicated firms were either raising prices or looking to do so, and that short-term inflation expectations remained elevated.
The statement also recorded the other side of the ledger. Output growth had slowed, housing prices had fallen in most capital cities, new housing loans had declined noticeably, and labour market conditions had eased broadly as expected. In light of these developments, the Board judged that a further tightening in financial conditions was warranted to support a return of inflation to target within a reasonable period.
The forward guidance shifted as well. The Board indicated that it remains prepared to raise the cash rate further if needed. Westpac described this as a small but meaningful change from the “if upside risks materialise” condition attached at the previous meeting.
The bypass that closed
The energy language in the RBA statement had a concrete counterpart in September. Saudi Arabia shut its East-West oil pipeline after the line was struck by drones launched from Iraq. The pipeline links fields near the Gulf to the Red Sea port of Yanbu, and according to data cited by Reuters, it had been moving four to five million barrels a day in recent months.
Its significance lies in what it was for. Since the conflict began, the pipeline had served as a route around the Strait of Hormuz, the chokepoint at the centre of our September outlook. The pipeline resumed operations at reduced rates on 22 September, and by early October, Bloomberg reported flows of close to six million barrels a day.
The episode adds a layer to last month’s observation. In August, the question was what happens when a single route carries a large share of global supply. In September, the alternative route was exposed to the same conflict. An alternative route reduces a risk only to the extent that it does not share it.
Thirteen days earlier, in Washington
The RBA was not the only central bank to tighten in September. On 16 September, the Federal Open Market Committee voted twelve to none to raise the federal funds target range by a quarter point to 3.75 to 4 per cent. It was the Federal Reserve’s first increase since July 2023.
The Committee’s statement was brief. It noted that uncertainty remained elevated, partly owing to geopolitical developments, and that inflation remained elevated. The projections released alongside it carried more information. Of the 18 participants, 16 projected a year-end policy rate above the current target range of 3.75–4.00 per cent, while two projected no further increase.
The Fed’s move and the RBA rate hike, thirteen days apart, point in the same direction. Both were taken with inflation above target and geopolitical developments adding to uncertainty.
What reached Australian prices
The day after the RBA rate hike, the Australian Bureau of Statistics published the August CPI. Annual inflation rose to 4.0 per cent, from 3.5 per cent in July, while trimmed mean inflation held at 3.6 per cent.
Much of the movement in the headline came from two items. Automotive fuel prices rose 14.8 per cent in August alone, which the ABS attributed to higher world oil prices and the unwinding of the remaining federal fuel excise relief. Electricity rose 13.2 per cent over the year, largely because Commonwealth electricity rebates had ended.
The pattern is worth comparing with last month. In July, the headline measure moved down while the trimmed mean held still. In August, the headline moved up and the trimmed mean again held still. Over two months, the top line has swung with fuel and rebates, while the underlying measure has not moved at all, and remains above the RBA’s 2 to 3 per cent target band.
The assumption question
September carries a second reading, and it has little to do with energy.
A consensus forecast is a snapshot rather than a fixed point. In the four weeks before the RBA rate hike, the expected path for Australian rates moved from an extended hold to a hike. Expectations are meant to respond to new data. What deserves attention is how much may quietly rest on them.
Many portfolio decisions embed a view on interest rates without stating it. The income expected from floating rate exposures, the cost of any borrowing inside a structure, the relative position of cash, and the valuation of longer duration assets all carry an assumption about where rates are heading. A portfolio can hold several different assets that all depend on the same assumption. When that is the case, the holdings list may look diversified while the underlying exposure is not.
What an October review can reasonably ask
Three questions follow from the month. None of them presupposes a conclusion.
First, which holdings rest on a particular path for interest rates, and how would they respond if expectations shifted again by a similar margin over a similar period.
Second, where does the portfolio rely on a single route for liquidity or income, and does the alternative share the same exposure. The pipeline that closed in September offers a useful frame for this.
Third, is the reasoning behind the current positioning recorded clearly enough to be revisited when the underlying assumptions change. A view that is written down can be tested. A view that is only implied is easier to overlook.
The next RBA decision is scheduled for 3 November, following the September CPI release on 28 October. The September RBA rate hike showed how quickly a settled view can change. The useful response is not a prediction about November. It is knowing which parts of a portfolio depend on the answer.
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