A record number of untaxed vehicles are being seized, according to the Driving and Vehicle Licensing Agency (DVLA).
The DVLA estimates that 1.55 million cars on Britain's roads aren't taxed.
It has recently launched a fleet of vans equipped with cameras that scan rows of parked cars, checking for tax details.
The DVLA estimates it's immobilising or towing away 400 untaxed cars a day.
Owners of clamped vehicles must pay an 80 release fee and provide valid tax and insurance documents, or risk having their vehicles crushed.
The length of time the owner has to prove their vehicle is taxed and insured depends on its value.
A car valued at 385 or under can be disposed of after seven days, but owners of a vehicle worth more than 385 have 14 days to act.