ASB is reviewing the ownership of its Aegis investment and custody business, which administers $15.2 billion of funds.
The bank says a strategic review will assess whether Aegis's potential could be better realised under new ownership.
The review, which is expected to take six months, continues a trend among Australian banks to sell assets – including financial advice and wealth management units – in the wake of the Australian Royal Banking Commission.
ASB tried to sell Aegis in 2010 but advanced talks with Pyne Gould Corp's then subsidiary Perpetual Group broke down.
In February this year ASB chief executive Vittoria Shortt told the Herald the bank was reviewing its operations following the Royal Commission report which was scathing of behaviour by institutions, including the bank's parent, the Commonwealth Bank.
Shortt said the bank was looking at which of the 76 recommendations could apply here.
Aegis was started by Sovereign Insurance in 1996 and became part of ASB in 1998. It manages local and offshore investments on behalf of banks, brokers, trustee companies and fund managers.
Adam Boyd, ASB's executive general manager for private banking, wealth and insurance, says the aim of the review is to test whether Aegis can better grow and improve its service to customers within ASB or under new ownership.
Aegis comprises two business, Aegis Ltd and Investment Custodial Services.
The firm says its custodial wrap service offers investors access to some products only available through investment platforms, and at wholesale fees and low brokerage. All portfolio transactions are managed and reconciled by Aegis, which also provides valuation, performance and tax reporting.