TLDR
Commonwealth Bank brought forward its rate-hike call to the Reserve Bank's 28-29 September meeting, citing Brent crude crossing US$100 a barrel. NAB shares the September view; Westpac holds out for November. A 25 basis point rise would add $91 a month to a $600,000 mortgage.
The oil shock that moved the call
Commonwealth Bank's Australian Economics team had pencilled in a later move. Then Brent crude crossed US$100 a barrel and the calendar shifted. CBA's Australian Economics team now expects the Reserve Bank to lift the cash rate 25 basis points to 4.60 per cent at its 28-29 September meeting, after oil climbed from roughly US$80 in August on the back of the Middle East conflict.[1]
"We now expect the RBA to hike the cash rate by 25 basis points to 4.60 per cent at its 28-29 September meeting," CBA's Head of Australian Economics, Belinda Allen, said.[1] The forecast is the public version of a model that also drives CBA's own funding plans, and when that model moves, variable rate pricing decisions tend to follow.
Oil feeds Australian inflation through petrol and freight costs. A sustained run above US$100 raises the risk of second-round price effects in wages and services, the exact dynamic the RBA has been watching since it last tightened.
Where the major banks stand
NAB arrived at the same September destination by a different route. NAB shifted its forecast to a 25 basis point September hike, taking the cash rate to 4.60 per cent, as early as late August.[2] Two of the four majors now share the same date and the same number.
Westpac stands apart. Chief economist Luci Ellis said the bank's base case remains a 25 basis point move in November, with the cash rate reaching 4.60 per cent then rather than next week. "Tactically, we believe RBA leadership would strongly favour a November hike over September," Ellis said.[3] Westpac's reasoning centres on the board's preference for more data before moving, particularly on housing and wages.
The timing gap carries margin consequences. Banks that call September correctly will have positioned their funding costs ahead of the move; banks that called November and are wrong absorb the difference in their net interest margins, at least briefly.
What the RBA has already signalled
Governor Michele Bullock gave markets enough to work with on 18 September. Bullock said "developments suggest that although growth in the Australian economy is slowing, some of these upside risks to inflation appear to be materialising."[5] That sentence falls short of a pre-commitment, but it makes a September move defensible to a board that prizes predictability.
The public narrative from the RBA has stayed cautious. The internal read from the bank economists is considerably less patient, particularly after oil moved the way it did through September.
What a hike costs borrowers
A 25 basis point increase adds $91 a month to repayments on a $600,000 loan with 25 years remaining, according to Canstar calculations.[4] Most owner-occupiers carrying a loan taken out between 2020 and 2022 still hold balances well above that $600,000 mark, so the real monthly impact scales higher for a large share of the market.
CBA flags a further rise to 4.85 per cent as a risk rather than a base case, citing a slowing economy, a labour market moving toward balance and a significant housing correction already under way.[1] The bank's internal view is that one more move is probably the ceiling, absent another commodity shock.
The Reserve Bank's Monetary Policy Board meets on 28 and 29 September 2026.
KEY TAKEAWAYS
SOURCES & CITATIONS
FREQUENTLY ASKED QUESTIONS
When does the Reserve Bank next meet to decide on interest rates?
Which banks expect a rate rise in September and which favour November?
How much would a 25 basis point rise add to a typical mortgage?
Could rates rise again beyond 4.60 per cent?
Vikram Singh writes about banking. He follows where money actually moves, from the strategy set in head office to what changes on a customer's phone.
