As part of the South Australian Government's crackdown, anyone convicted of winding back an odometer will soon face imprisonment for the first time of up to two years or a fine of up to $30,000 - up from $10,000.
The fine for anyone convicted of unlicensed second-hand car dealing for a first or second offence will increase from $100,000 to $150,000.
For subsequent offences, potential jail time will increase from one year to two years, and the fine will increase from $100,000 to $250,000.
For body corporates, the fine will be up to $500,000.
Second-hand vehicle dealers must have a licence if they buy, sell or offer for sale four or more vehicles in 12 months.
The harsher penalties follow a rise in complaints about unlicensed dealers selling from home via sites such as Facebook Marketplace and engaging in dodgy practices including selling with false papers and winding back the odometer.
Licensed dealers operating both from home and in car yards have also been caught winding back odometers.
RAA Mobility Expert Mark Borlace welcomed the tougher penalties and offered advice to prospective second-hand car buyers.
"A car is often the second largest investment a family or person might make after their house – so we’re potentially talking about a large chunk of their hard-earned savings," Mr Borlace said.
"When buying a used car, the odometer is one of most obvious ways to gauge how much life is left in the car and if that has been tampered with then you might be buying a car that may have expensive repairs waiting for you.
"RAA’s advice is to get the vehicle inspected by a trusted mechanic before purchase as that might be the cheapest form of pre-emptive insurance you could have."
In the past financial year, six individuals have been convicted of tampering with odometers, facing a total of more than $35,000 in fines and compensation orders. Of those, four were unlicensed.
Consumer and Business Services is asking members of the public to report any vehicle dealer – licensed or unlicensed – whom they suspect of illegal behaviour.
To report concerns about suspect second-hand vehicle dealers, contact Consumer and Business Services.
