ANZ is facing a hefty payout after its customers recorded a partial victory in a multi-million dollar legal battle against the bank's fees.
The Federal Court ruled on Wednesday that the bank had been illegally imposing penalties for late payments on credit cards.
Justice Michelle Gordon agreed with lead plaintiff Lucio Paciocco's argument that the fees were "extravagant, exorbitant and unconscionable", and represented a breach of contract.
But Justice Gordon also ruled in ANZ's favour by dismissing claims that other types of bank fees were illegal penalties.
Such fees included honour and dishonour fees ranging from $20 to $45, over limit charges and non-payment fees.
Justice Gordon deemed those fees not a penalty and not a breach of contract.
The parties are to meet to again next week in relation to costs.
a funder of the legal action, IMF, said in a statement that late payments on credit cards constituted about 25 per cent of all claims brought by members of the class action.
The ruling has wider implications, with the ANZ case only the first of eight planned class actions involving 185,300 customers of eight lenders, claiming $243 million in damages.
Law firm Maurice Blackburn, which is representing the bank's customers, has previously suggested that if it wins it could then involve potentially millions of bank customers hit by billions of dollars in fees.
Justice Gordon's ruling effectively means ANZ was not entitled to charge an extra cost of between $20 and $45 if a customer did not pay their minimum credit card bill on time, because it represented an illegal penalty and did not reflect its true cost.
ANZ had admitted that it had breached its contract by charging those "exception" fees, Justice Gordon said.