Suncorp is to refund $A23 million to customers after a review by the Australian Securities and Investment Commission found it failed to provide promised discounts on insurance products.
ASIC said problems with the banking and insurance company's IT, human resources and sales systems have affected more 849,000 life insurance and general insurance customers since June 2008.
The ABC reports that the problems led to the company failing to provide promoted discounts to seniors card holders and customers who with multiple insurance policies.
It also failed to inform some customers of significant upgrades to their policies.
ASIC deputy chairman Peter Kell said Suncorp had agreed to overhaul its IT and sales processes.
"Suncorp acted appropriately in reporting the breaches to ASIC as it identified them, and in acting to remediate affected customers," he said in a statement.
"ASIC is pleased Suncorp is improving its compliance systems in a way the review suggested."