Greater Bank chief executive officer Scott Morgan said reviews showed no systemic issues with the way the bank calculated its mortgage offset accounts, but 31 customers had to be repaid a total of $56,000 after a human-error related problem was found.

Confirmation of the number of affected Greater Bank customers came after the Newcastle Permanent apologised to 18,000 customers this week after overcharging them more than $4 million because of "mistakes" with mortgage offset accounts.

Mr Morgan said reviews showed "we don't have problems with mortgage offset accounts".

"We've got no appetite to hide problems. We just get on and fix them when customers raise problems with us," Mr Morgan said.

"When issues are raised we try to make sure that it's not a systemic issue. We made sure there were no systemic issues relating to mortgage offset accounts, picked up a human-related error and made adjustments."

In a statement to the Newcastle Herald on Wednesday the Greater said it was one of many Australian financial institutions "invited to address a series of questions from the royal commission, primarily focused on 'misconduct' in the industry".

"The due diligence process resulted in a positive outcome for Greater Bank, with no systemic misconduct, other systemic conduct or behaviour considered below community standards and expectations identified within Greater Bank's procedures and operations," the Greater statement said.

In its annual report in 2019 the Greater said the banking royal commission had shone a light on governance standards and operational conduct within the industry.

"While much work is now being undertaken by the industry and our regulators as a result of the commission's findings, for the majority of customer-owned banks, building societies and credit unions in Australia it is business as usual," the annual report said.

On Wednesday the Newcastle Herald revealed the Newcastle Permanent will repay 18,000 customers overcharged more than $4 million because their offset transaction accounts were incorrectly linked to their home loans.

The building society declined to comment about whether it tried to limit the damage after acknowledging the issue and apologising to customers in its annual report in mid-October, but failing to mention the apology in a media release about the annual report.

The Australian Securities and Investments Commission said offset accounts were savings or transaction accounts linked to home loans which helped reduce the amount of interest customers paid on their mortgage. If a mortgage's outstanding balance is $300,000, and there are $50,000 savings in an offset account, interest is only payable on $250,000.

In 2017 the National Australia Bank refunded $1.7 million to 966 home loan customers after failing to properly link offset accounts to home loans written by mortgage brokers.

In 2019 the NAB said another 4930 were identified as needing compensation because of mortgage offset overcharging, taking its total payout to more than $8 million.

In 2014 the ANZ Bank said it would repay an unknown number of mortgage offset account customers $70 million in compensation, but by October, 2019 the bank was still working through a backlog of accounts.

ANZ customers from as early as 2003 had been overcharged because of incorrect links with mortgage offset accounts.

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