More than 40,000 NAB customers have so far joined the action, which is part of a broader legal stoush with the major lenders over bank fees – the biggest in Australian history.

Customers now have until 4pm Tuesday to sign up to receive any potential compensation from NAB after the court agreed to re-open registration in November as part of a possible settlement.

The decision puts the spotlight on other banks over whether or not they will follow suit.

ANZ became the first victim of the mass class action over bank fees in February last year when the Federal Court ruled it had charged "extravagant, exorbitant and unconscionable" late payment fees on credit cards.

While the court found late fees were illegal, it ruled in favour of the bank on other fees.

Both Maurice Blackburn, which is representing customers in the action, and the bank are appealing the decision.

The case against ANZ is being used as a template for action against nine other major lenders, including the Commonwealth Bank, Westpac and Citi.

All banks face massive payouts if an appeal rules in favour of customers.

NAB announced in November that it was moving towards a settlement in the class action, with an application seeking to open and close the case over "exception" fees including penalty, dishonour and overdrawn fees.

James Middleweek, managing director of Financial Redress, a subsidiary of IMF Bentham, which is funding the action, said he welcomed NAB's decision.

"It's high time that the other banks followed suit," he said.

Mr Middleweek said a survey of 1026 people, commissioned by Financial Redress, showed the banks were charging Australians more than what they considered "fair" and twice as much as they thought they were paying.

"Most consumers understand the fairness of paying a reasonable fee when it reflects the bank's costs. However, they object to being hit with an excessive fee, especially when it appears unlinked to the amount in question or the time period involved," he said.

A NAB spokesman said there was no further update on a potential settlement and declined to comment on negotiations with Maurice Blackburn.

The class action over bank fees against the major lenders is being described as the largest class action in Australian history, with around 185,000 customers from different banks registering to become members.

The Federal Court's decision centred on a ruling that despite charging customers penalties of up to $35, the cost of handling late payments for the bank was as little as 50¢.

ANZ is appealing the decision, claiming regulation costs push this figure much higher.

The late fee case, if successful, could cost the banks up to $240 million in refunds to customers. If other fees are determined unconscionable, the payouts could escalate to several billion, proponents say.

The Federal Court ruling also significantly threw out ANZ's six-year statute of limitations, meaning anyone who has ever been charged a late fee by ANZ could potentially come forward and claim those fees back.

Maurice Blackburn is appealing key parts of the ruling that favoured ANZ – that honour fees, ­dishonour fees, and over limit (overdrawn) fees are acceptable.