Australia’s largest class action case in history began Tuesday with thousands of consumers fighting against $231 million in bank fees, the Agence-France Presse reported.

The lawsuit against the Australia and New Zealand Banking Group (ANZ) is part of a larger class action litigation against eight major lenders, with arbitrator Sydney offices claiming more than 170,000 consumers received  penalty charges that were excessive and illegal.

The case, which may have enormous ramifications for consumers, will focus on fees for services like account overdraws were disproportionate to what the back pays to provide them.

According to documents filed with the High Court on behalf of 38,000 ANZ customers, the case hinges on a “variety of fees for overdrafts, overdrawn accounts, dishonor fees and over-limit credit card accounts”.

The lower-level Federal Court ruled in December that only four classes of fees falling under ANZ’s late payment schedule relating to credit cards merited being characterized as a “penalty” that could be contested in court.

ANZ was cleared over four other classes covering over-drawing from accounts and having insufficient funds to make scheduled payments, in the case first launched in 2010.

The mediation Sydney firm representing the customers, has appealed to the High Court seeking a broader finding of what constitutes a penalty in the hopes of expanding the case against the banks. ANZ had welcomed the earlier ruling, which was largely in its favor, and said it would vigorously defend itself.