The Commonwealth Bank will hand back a massive $80 million to customers after discovering it failed to apply fee waivers and other benefits to which they were entitled.
About 216,000 customers will receive an average of $370 each in the biggest compensation payout by one of the major banks this year.
CommBank's latest refund relates to staff failing to apply interest rate discounts, fee waivers and other benefits to Wealth Package home loan customers.
Other mistakes by the major banks, which delivered combined annual cash earnings of $30 billion in 2015, have involved home loans, insurance policies, financial advice, agribusiness and wealth management accounts.
"This was a significant breach, and shows how important it is for licensees to have robust systems in place to ensure financial products deliver the benefits that consumers have paid for," ASIC deputy chairman Peter Kell said.
"Manual processes to apply discounts, waivers and other concessions involve inherent compliance risks. Licensees should carefully consider whether those risks are being appropriately managed, or are capable of being appropriately managed."
The bank, which is also working through about 8,000 complaints related to allegations customers lost savings due to its poor financial advice, began contacting affected customers in October.
CommBank says it expects to have all those affected by the latest lapses, which began in 2008, compensated by the end of this year.
Matt Comyn, group executive, retail banking services, apologised to customers for the mistake and said the bank had taken steps to address the root cause of the errors.
"Once we discovered the error we notified the regulator, ASIC. We worked to identify those customers who were due a refund, and the amount owed to them, including interest," he said.
"Whilst we will always do our best to minimise errors, this shows our commitment to proactively identify any historic errors, and put them right."
ANZ this month said it will $13 million in compensation to 200,000 customers after failing to pay them enough interest on their savings accounts.
National Australia Bank, Macquarie Investment Management and Bank of Queensland have also recently compensated customers.
COMPENSATION PAY DAY FOR BANK CUSTOMERS
* Nov 2015 - CBA refunds $80m compensation to 216,000 Wealth Package customers after failing to apply discounts
* Nov 2015 - ANZ offers $13m compensation to 200,000 savings account customers after failing to pay them enough interest
* Oct 2015 - CBA refunds $7.6m to agribusiness customers for interest rate and fee errors
* Oct 2015 - Westpac offers unspecified refunds to 10,600 insurance customers who paid for cover they didn't need
* Jul 2015 - NAB pays out $25m to 62,000 wealth management customers who were short-changed
* Jun 2015 - Macquarie Investment Management refunds $5.5m to 2,300 customers overcharged in fees
* Apr 2015 - ANZ pays back $30m to 8,500 customers who missed annual reviews from financial advisors
* Aug 2013 - Bank of Queensland refunds $34.5m to 38,000 customers who were overcharged fees and underpaid interest
