Approximately $5 million will be refunded by ANZ to around 25,000 customers, including pensioners, after the bank has miscalculated their account fees.

The corporate watchdog announced on Wednesday that the bank had not properly applied fee reductions and waivers for customers who held an Access Basic account, a consumer credit card or an Everyday Visa Debit Card since 2007.

The Australian Securities and Investments Commission released a statement saying that unreliable manual processes and problems with the interaction between automated and manual processes had caused the issues.

The Access Basic account is aimed at low income customers such as pensioners and those holding a Centrelink Health Care card.

“ANZ’s Access Basic account is specifically designed for low income consumers who are unable to pay high account fees,” ASIC deputy chairman Peter Kell said.

“This matter highlights the importance of appropriately managing manual processes to apply fee waivers and discounts, and designing and maintaining robust systems to support such features.”

The bank alerted ASIC to the problem, and a permanent automated waiver system which eliminates the need for manual intervention has now been implemented. Customers who are due a refund of account fees will also be awarded an amount of interest.