Kiwibank is facing criminal charges after overcharging customers $7 million.
The Commerce Commission alleges more than 36,000 customers were overcharged fees and interest rates on home loans, credit cards and overdrafts over a period of several years.
Deputy chair Anne Callinan said these were serious charges stemming from multiple errors in Kiwibank's manual and electronic systems, which resulted in the bank misrepresenting what customers owed.
"In the Commission's view these are longstanding, systemic breaches of the Fair Trading Act some of which date back to Kiwibank's inception in 2002," Callinan said, adding the charges related specifically to overcharges from 2019.
"Lenders must have processes in place to ensure consumers are getting a fair deal and are charged what was advertised to them.
"The commission expects banks to make the necessary investment in the systems that support their compliance obligations so they get things right for consumers."
The issues were first identified by Kiwibank and reported to the commission.
It reported the overcharges to the commission and has been contacting affected customers and progressively refunding overcharges.
The commission said it could not comment further as the case is before the court.
