Of the more than 3 million Australian households that have a mortgage, more than half feature an offset account.

When used properly, these accounts can help borrowers save thousands yearly by reducing the outstanding loan balance, which in turn decreases the interest charged.

There is some $300 billion sitting in offset accounts across Australia.

However, 9News has uncovered that the Australian Securities and Investments Commission (ASIC) is worried that due to bank errors, customers may not be receiving the savings they should be.

“We’ve heard, in some instances, the banks have not connected the offset account to someone’s mortgage account,” commissioner Kate O’Rourke said.

“That’s bad for the consumer, but we’re not sure how widespread that problem is.

ASIC has initiated a monitoring program involving eight banks, including some of the major four, and there is a possibility of refunds if it is determined that customers have not been receiving their rightful savings.

“Our expectation is that when things have not been properly done, consumers are remediated,” O’Rourke said.

The investigation could take a year to find out how many people have been impacted.

For now, consumers are encouraged to thoroughly examine their statements and contact their bank to verify that their accounts are correctly linked if they have any concerns.