Dacorum Council has carried out safety checks on taxis throughout the borough.
Six out of the 18 taxis stopped in the borough were found to have faults, including damaged bodywork and out-of-date fire extinguishers.
The operation, carried out by Hertfordshire Police and Dacorum Council, took place between 4 and 10pm on Thursday April 3.
Councillor Neil Harden, portfolio holder for residents and regulatory services said "We hope these checks will act as a reminder to the owners of all licensed taxis and private hire vehicles to carry out regular safety checks on their vehicles. Vehicles must be kept to the high standards expected by the council, and we will take action where these standards are not met."
Dacorum Council’s anti-fraud team were also checking drivers for fraudulent benefit claims.
All vehicle owners with faults were given formal notices and will need to repair the faults or their licenses could be suspended.