Bank of Queensland (BOQ) will broaden a review into its compliance systems and remediation processes, at the request of the Australian Securities and Investment Commission
In a statement, ASIC said the development comes after further reports of errors in the lender's interest rates and fees.
The lender self-reported a $12 million customer error to ASIC last year, following a system issue.
As a result of ASIC action, Bank of Queensland appointed an independent expert to make sure its compliance systems were effective and customers were refunded.
It was revealed in August the review had uncovered further errors, some dating back to 2004, resulting in customers being overcharged in fees and underpaid in interest.
The bank confirmed that it would refund an additional $34.5 million and pay another $11.5 million to fix these additional errors.
"We want to make sure the expert’s review leaves no stone unturned and all customers are appropriately compensated," ASIC deputy chairman Peter Kell said.
"The review will also ensure that any necessary compliance system improvements are made to minimise the occurrence of similar errors in future."
Bank of Queensland will report to ASIC regularly over the coming year.