Admiral has agreed to contact customers who may have been given inaccurate information in renewal documents.
This follows the new rules introduced by the Financial Conduct Authority (FCA) in April this year which require firms to show clearly the insurance premium a customer paid last year alongside their proposed renewal premium.
The regulator stated that it had found that Admiral included inaccurate premium amounts in renewal documents issued to some customers.
According to the FCA, Admiral will now make changes to ensure it is fully compliant with the new rules.
Admiral has agreed with the FCA to contact customers who have renewed their policies after 1 April 2017.
In addition, if affected customers choose to go to another insurer as a result, they will be able to cancel without penalty and will have their premium refunded.
The watchdog noted that it is currently assessing firms’ implementation of these rules to ensure customers are given clear and fair disclosure on their renewal prices.
It added that it had seen good practice from companies in the sector, but warned that it had also found some concerning examples and will continue to address specific concerns with individual businesses.
Jonathan Davidson, executive director of supervision- retail and authorisations at the FCA, said: “It is vital that insurers give customers the right information so they can easily compare premiums and make a choice whether to shop around.
“When introducing these measures, the FCA was clear that firms should be ready from April 2017.”
He concluded: “We will continue to keep a close eye on the industry’s response to ensure firms are complying with the new rules and will take action where necessary.”