Hertz also conceded that between January 2013 and August last year it had charged customers for repair costs it falsely claimed was the cost borne by the company.

In fact, Hertz received spare parts at a discount and did not pass on any savings. In cases involving windscreen or tyre repairs or replacements, the cost to Hertz was much lower than the amount charged to customers.

Hertz is refunding, or has refunded, $152,000 to more than 700 customers. Many of these customers are yet to be identified and contacted about the refund.

"This case serves as a message to vehicle rental companies that they must have robust compliance procedures in place to ensure they do not contravene the Australian Consumer Law by incorrectly charging customers for damage they are not responsible for," said ACCC deputy chair Michael Schaper.

"Vehicle rental companies must also ensure that they are transparent and accurate in communicating with their customers about the charges they are applying for vehicle rentals and repairs."