An offset account is one of banking’s simplest promises: keep money in this account and the bank calculates mortgage interest on a smaller balance.
ASIC’s July review found banks did not always keep that promise. Across eight banks representing more than 70% of Australia’s home-loan market, it found weaknesses in setup, monitoring and management. Reports made to ASIC for the two years to August 2025 included more than $55 million in customer compensation for offset failures.
The balance was visible. The loan was visible. The link between them was not always working.
A relationship can fail silently
If a debit card stops working, the customer notices at the checkout. A disconnected offset account is quieter. Mortgage repayments may remain unchanged while too much interest accrues each day.
ASIC found examples of accounts not being opened, not being linked, being linked late or becoming disconnected after a loan change. Manual processes were a recurring weakness. Some banks struggled to identify offset requests and were inconsistent in detecting failures.
This is a master-data problem with a dollar sign attached. The bank needs a valid relationship between customer, eligible loan and nominated transaction account. Every refinance, product switch and servicing request can alter that relationship. If systems do not prove the link remained intact, they are relying on absence of complaints as a control.
The control should calculate both ways
A decent reconciliation would not merely confirm that an offset flag exists. It would independently calculate expected interest using the offset balance and compare that result with interest actually charged.
Exceptions should be visible at customer level and portfolio level. If a particular loan migration generates a cluster of breaks, the bank should find the pattern before customers do. Compensation also needs its own control: affected dates, balances, interest rates, fees and time value must be reproducible.
Customers should be able to see the benefit in digital banking or on a statement. Transparency is not a substitute for correct processing, but it gives both sides a chance to spot an error.
The Payment Nerd view
Reconciliation is often treated as something that happens after a payment. This case shows the wider job. Banks also need to reconcile product promises against the calculations their systems actually made.
Australia had about $349.1 billion sitting in mortgage offset accounts in March 2026. At that scale, a small percentage of broken links can create a very large remediation.
The technology failure was not that the bank lost the balance. It was that two correct balances were combined incorrectly. That is exactly the sort of quiet operational error good controls are meant to catch.
Sources: ASIC mortgage offset review; ABC News, 29 July 2026.