Dishonest car dealers who posed as private traders or dodged other rules have been fined by the Commerce Commission.

Three dealers have picked up $1000 fines after failing to show key information about the vehicle they were selling, or for failing to disclose their status online.

Consumer Manager Stuart Wallace says buyers can take heart from the crackdown.

"Now we can just issue infringement notices and it's a short sharp reminder that the law needs to be complied with."

He says consumers need to know they're getting a fair deal.

"A motor vehicle purchase is a big purchase for consumers and so it's really important that all the essential information about the car is right there in front of them."

So far eight fines have been handed down to three separate dealers in Auckland and Christchurch.