Commonwealth Bank said it has refunded A$4.9 million to around 10,800 customers after its Bankwest division "failed to link offset accounts to home loan accounts for some customers who had opened accounts between 2007 and June 2016, resulting in customers being overcharged interest."The Australian Securities and Investments Commission spelled out Bankwest's mistakes, and the remedy, in a media release yesterday.ASIC said that "following media coverage of ASIC's work in relation to similar breaches by another bank, Bankwest undertook an internal investigation into the operation of its offset accounts."It said Bankwest "identified issues in the linking of offset accounts with home loans and reported the matter to ASIC as a significant breach of its licence."