Foreign exchange markets head into October navigating shifting central bank expectations, inflation sensitivity and uneven economic growth across major economies.

At the time of writing in mid-September, the Reserve Bank of Australia (RBA) cash rate is 4.35%. The Federal Reserve (Fed) raised its target range by 25 basis points (bps) on 16 September to 3.75% to 4.00%, while the European Central Bank (ECB) raised its deposit facility rate to 2.50%, effective 16 September.

The Bank of Japan (BoJ) entered its 17 to 18 September policy meeting with its overnight call rate target at around 1.00%. That setting should be refreshed against the September decision before publication.

These central bank settings reflect different regional inflation and growth conditions. They also leave interest-rate differentials firmly in focus as markets assess what comes next.

The Australian dollar (AUD) continues to draw support from Australia's relatively high policy rate, while the Japanese yen (JPY) remains sensitive to the gap between Japanese and overseas yields. But recent price action has not been one-way, making incoming central bank guidance and economic data important for October.

Quick facts

The Fed meets on 27 to 28 October, the ECB on 28 to 29 October, and the BoJ on 29 to 30 October. The next RBA decision is scheduled for 3 November.

Selected currency snapshot

Australian dollar: yield support remains in focus

The Australian dollar has drawn support from Australia's relatively high policy rate, although recent moves also show how quickly global yields and US dollar strength can offset that advantage.

The RBA cash rate remains at 4.35%, compared with the Fed's 3.75% to 4.00% target range and the ECB's 2.50% deposit facility rate.

The RBA has continued to emphasise that inflation remains too high and that risks to the inflation outlook are tilted to the upside. That leaves the Australian dollar sensitive to incoming inflation and labour-market data.

The Australian Bureau of Statistics (ABS) has scheduled the September Labour Force release for 15 October at 11:30 am AEDT and the September CPI release for 28 October at 11:30 am AEDT.

Risks and constraints

The Australian dollar's interest-rate advantage does not operate in isolation.

Changes in Asia-Pacific growth can affect commodity demand, while shifts in global yields and risk sentiment can quickly alter capital flows.

Softer Australian activity or weaker commodity demand could weigh on the currency. Conversely, firmer domestic inflation could affect expectations for the RBA policy path.

That leaves the AUD balancing domestic rate support against global growth, commodity and US dollar forces.

Japanese yen: the yield gap still matters

The Japanese yen remains highly sensitive to relative interest rates and international bond yields.

The BoJ entered its September meeting with the overnight call rate target at around 1.00%, materially below Australian and US policy rates.

That gap remains relevant for carry-trade positioning, where investors borrow in lower-yielding currencies to gain exposure to higher-yielding assets.

But the relationship is not static.

The yen can strengthen quickly when Japanese rate expectations rise, US Treasury yields fall or risk sentiment deteriorates. Recent September trading has already demonstrated that the currency can move sharply in both directions, as highlighted in previous commentary on the AUD/JPY rate divide.

Japan's Statistics Bureau has scheduled the September national CPI release for 23 October. The BoJ's October meeting is scheduled for 29 to 30 October.

Risks and constraints

Rate differentials remain important, but they are not the only driver of the yen.

A shift towards tighter BoJ policy could support Japanese yields and narrow the gap with overseas markets. Falling US Treasury yields could have a similar effect from the other direction.

Periods of broader risk aversion may also encourage the unwinding of carry trades, which can generate rapid moves across JPY pairs.

That makes incoming inflation data, bond yields and BoJ communication important inputs for October.

AUD/USD: the policy gap in focus

AUD/USD provides a useful benchmark for comparing Australian monetary policy expectations with incoming US economic data.

Australia's cash rate is currently 4.35%, while the US federal funds target range is 3.75% to 4.00%.

That differential can provide support for the Australian dollar, but it does not determine the exchange rate on its own.

Commodity demand, global equity sentiment, US Treasury yields and changing expectations for both the RBA and Fed can all influence AUD/USD.

What could shift the outlook?

AUD/USD enters the October period with an Australian policy-rate advantage, but changes in US yields and global risk sentiment could offset that support.

Stronger Australian inflation or employment data may reinforce expectations that domestic policy remains restrictive. Softer Australian data could have the opposite effect.

In the US, stronger employment or inflation data could reinforce expectations for tighter policy, while softer readings may reduce those expectations.

That leaves the pair sensitive to the relative direction of Australian and US data, rather than any single release.