Most of the complaints were in relation to unknown fees. "Our dealings with Hertz in Brisbane has been a very frustrating experience. They have our credit card number so they can charge what they like and we have to fight this. "It's difficult to resolve the problem from halfway around the world. Overseas customers are at a huge disadvantage." Despite the Hertz undertaking and the $100,000 penalty slapped on Europcar for its "unfair and void" contract terms in April, ACCC chairman Rod Sims said he was "unfortunately confident" more was needed to bring the industry into line. "We've seen over recent years bad behaviour ... I think this has been going on for long enough. We are going to continue working with them to get change," he told Fairfax Media.

Hertz says John and Pauline Pearson damaged a hire car and charged them more than $3000. "My experience tells me we may well need to take more action for the industry to take sufficient notice." Hertz has refunded 283 customers about $243,000 between January 2014 and August 2015 in relation to incorrect pre-existing damage charges. Hertz has committed to identifying more customers affected between 2013-2015. ACCC chairman Rod Sims. Credit:Michele Mossop Mr Sims has urged Hertz customers who believe they have been unfairly charged for pre-existing damages outside the ACCC's 2013-15 investigation period to contact Hertz.

"If Hertz think there's a real chance their systems, back then, allowed people to get charged for pre-existing damage, then I think they should be looking at these matters, giving the customer the benefit of the doubt," he said. Wine writer Huon Hooke challenged Hertz about two false damage charges. Both were waived. Each time I energetically challenged them and both times they repaid the money into my credit card account without any reply, let alone apology. Huon Hooke "It's the right thing to do morally and the right thing to do from a business perspective." A Hertz spokesman said customers who believe they have been incorrectly charged for pre-existing damage should contact them.

"If a shortcoming in past processes is identified to have impacted a rental, then Hertz will address this directly with the relevant customer," he said. "Hertz supports industry-wide standards for all car rental providers in Australia and would welcome the opportunity to continue to work with the ACCC." In NSW, the number of complaints about car hire companies has doubled to 380 in 2015 compared with five years ago, according to Fair Trading. Most of the complaints were in relation to unknown fees, charges higher than the quoted price and obtaining refunds. The ACCC's investigation focused on charges for pre-existing damage and overcharging of repairs because of the high number of complaints.

Chris Bayley, from independent car rental insurer RentalCover.com, said he wants to see the ACCC investigate other rorts, including waivers with exclusions for common repairs such as windscreens and tyres, and non-refundable excessive fees such as "premium location surcharges". "[I'd like to see the ACCC investigate the fact they're] refusing to publish their 'not at fault' policies within their rental terms," he said. "If their driver is determined through the normal auto insurance subrogation process to be the party that did not cause the accident, we believe the renters should always be refunded for all excess charges that have been paid." Fairfax wine columnist Huon Hooke said he twice challenged false pre-existing damage charges by Hertz at Melbourne Airport in 2004, totalling $2000, and had them both waived. "Each time I energetically challenged them and both times they repaid the money into my credit card account without any reply, let alone apology or explanation."

Sydney retiree Ricardo Hora, who hired a Hertz car through his employer in 2007, said he successfully had an incorrect $1000 charge for damage he did not cause waived. "I spent a week or so in contact with Hertz and they were adamant that it was my fault," he said. "I told them I was going to refer the problem to my company's legal and the next day I got a call informing me the charge had been waived." A Fair Trading spokeswoman advised car rental customers to carefully read the contract and thoroughly inspect the vehicle before driving away. "Also check the vehicle thoroughly in the presence of the hire company when [you] return it," she said.