The Society of the Irish Motor Industry has launched a guide to help people understand the new Vehicle Registration Tax system being introduced in July.
Under the new system new cars will be taxed according to their Co2 emissions rather than the vehicle engine size.
The annual motor tax will also be linked to the emissions of the vehicle.
An online calculator has been developed on the SIMI website.
The Director General of SIMI, Alan Nolan, said consumers and dealerships are confused about the new system.
He said people should research the implications for themselves before they buy a new car.
SIMI is advising people to visit their website and shop around before buying a new or used car.