Commonwealth Bank of Australia unit Bankwest refunded A$4.9 million to customers for overcharging interest on home loans, the Australian Securities and Investments Commission said.

The regulator said in a statement that Bankwest refunded about 10,800 customers more than A$4.9 million after failing to link offset accounts to home loan accounts for customers who had open accounts from 2007 to June 2016. The mistake resulted in customers being overcharged interest.

An offset account is a savings or transaction account that, when linked to a home loan, offsets the balance of the loan account, reducing the interest payable.

Bankwest has since updated its systems and processes, including the automatic linking of new offset accounts, ASIC said.

As of Feb. 1, US$1 was equivalent to A$1.32.