The cash rate, in Australia, is the interest rate on unsecured overnight loans between banks. The Reserve Bank of Australia (RBA) sets a cash rate target to guide this market rate as part of monetary policy. A quant using “the cash rate” must identify which series is meant: the announced target and the published market benchmark can differ.
Four rates that should stay separate
| Rate | What it represents |
|---|---|
| Cash rate target | The RBA Monetary Policy Board's chosen policy rate target. |
| Published cash rate | The overnight unsecured interbank benchmark administered by the RBA, also known in financial markets as AONIA. |
| Interest rate on Exchange Settlement balances | An administered rate paid by the RBA on banks' settlement balances held with it. |
| Customer loan or deposit rate | A bank's price for a particular household or business product. |
Exchange Settlement (ES) balances are the funds banks hold at the central bank to settle payments with one another. Interest paid on these balances is distinct from interest negotiated between banks. A mortgage borrower participates in a different market again. See the RBA's implementation explainer.
The published benchmark normally uses a volume-weighted average of eligible cash-market transactions identified through the RBA's settlement system, RITS. It is rounded to two decimal places in percentage-rate terms. Specified fallbacks apply when transaction data are insufficient or technical problems occur; a published value need not always be a fresh transaction average. The RBA methodology defines the eligible market and publication rules.
A small difference, measured correctly
Consider a fictional Australian trading day, with annualised rate quotes:
- Cash rate target: 4.00% per annum.
- Published overnight cash rate: 4.02% per annum.
The market rate is 0.02 percentage points above target, equivalent to 2 basis points. In decimal-rate units:
This is a comparison between two rates for the same day. It is not a policy increase from yesterday, and neither annual quote means that a bank pays that percentage of principal for just one night.
Original schematic using fictional rates. The two numerical quotes describe the target and market benchmark; no ES interest rate or customer loan rate is assumed.
A positive gap alone does not identify a policy shock or prove an implementation failure. Its interpretation needs the operating framework, market conditions and data-quality notes.
How the target influences the market
The RBA influences banks' incentives through the terms on which they hold and obtain ES balances. Those operating arrangements can evolve. In its 25 August 2026 account, the RBA described a transition from high, supply-driven reserves towards a demand-driven ample-reserves framework, using full-allotment open market operations. It explicitly separated this operational transition from the monetary-policy stance. That dated account is more useful than assuming every cash-rate system has one permanent corridor width. See The Road to Ample.
The cash rate influences customer borrowing and deposit rates, but pass-through need not be immediate or equal. Funding conditions, competition and borrower risk also affect those rates. The RBA's transmission explainer explains why spreads can change. A cash-rate target is therefore an input to a funding model, not a substitute for the actual rate on a loan.
Using the series in a model
Keep the target, benchmark and customer rate in separately named fields, with their units and dates. For an event study, distinguish the decision announcement from the date the new target takes effect. For an overnight benchmark, distinguish the trading date from its publication date.
Under the RBA's published methodology, a day's cash rate is normally released the following business day. Check its actual availability time and any fallback or republication flag before joining it to returns. Using the final historical series as though it were already known on the trading day creates look-ahead bias.
Sources
- RBA — Cash Rate Methodology: Overview, updated 21 July 2026; definition and sections 1, 3–5.
- RBA — How the Reserve Bank Implements Monetary Policy, cash market, ES balances and future implementation system.
- RBA — The Road to Ample: Towards a Demand-driven Liquidity Regime, 25 August 2026; introduction and transition discussion.
- RBA — The Transmission of Monetary Policy, first stage and variable spreads.