Australia's biggest superannuation fund has revealed that it has been double charging some customers, and will refund around $70 million in fees and insurance costs to about 100,000 people.
AustralianSuper started internally investigating one year ago whether it had customers who inadvertently had multiple accounts going back as far as 2013.
"The fund regularly identifies and combines multiple accounts held by a single member to help those members avoid extra fees," a statement on Friday said.
"Following our review, we identified that our processes did not cover all instances of multiple member accounts."
That means it had members with multiple accounts who were potentially paying double lots of fees and insurance.
As a consequence, about 100,000 past and present customers will now be refunded about $650 on average each.
ABC News understands some of the money that could be refunded to customers could also include losses they might have made by having funds across multiple accounts.
The fund says it has informed regulators.
On Friday afternoon, ASIC said in a statement that it was "engaging with AustralianSuper in relation to the issues identified in its review".
ASIC said it had separately conducted a review of superannuation trustees' policies and processes surrounding their legal duty to identify multiple accounts.
"The review originated in response to an analysis of data that identified a high proportion of members with multiple superannuation accounts and ASIC started engaging with trustees in early 2022," the statement said.
"ASIC has engaged closely with APRA on this review and intends to release public communication in the coming months which covers our overall observations on compliance with section 108A by superannuation trustees.
"ASIC will continue to monitor AustralianSuper's planned remediation for affected members and uplift to processes."
APRA has also been contacted for comment.
Customers to be contacted in 'coming months'
AustralianSuper is a non-specialist fund that manages almost $290 billion in retirement savings for 3.1 million Australians.
In its statement, it said impacted customers will be contacted in "coming months".
"This should not have happened, and we apologise unreservedly to members," its statement said.
"The Fund is taking appropriate remediation actions and has self-reported the issue to the regulators."
An advocacy group for people with superannuation funds says the revelation by AustralianSuper is "alarming".
"Paying extra fees and insurance premiums for more than one account really adds up," Super Consumers Australia deputy director Rosie Thomas says.
"The Productivity Commission found having unnecessary multiple accounts can leave someone over $50,000 worse off in retirement.
"It's important we fix this problem across the super system, and getting funds to sort out intra-fund consolidation is the first step."
ABC News understands AustralianSuper investigated the possibility of double-up charges back to 2013 as this is when the relevant legislation applies.
"The laws to encourage super funds to get rid of multiple accounts within their own fund are a decade old," Ms Thomas said.
"We've never seen any public statement or actions from the regulators on this issue. It is alarming that such a major player is only discovering issues now."
Super Consumers Australia is now calling for a review of this issue into all superannuation funds.
