The Vehicle Checker will use the DVLA vehicle data to determine if the vehicle is compliant. The vehicle will need to meet the minimum emission standards of the zone to be compliant and not pay Clean Air Zone charges. Alternatively, you can apply for a local exemption. If you believe your vehicle is incorrectly recorded by DVLA you should approach them directly (You can contact the DVLA on 0300 029 8888 between 08:00-19:00 Monday to Friday and Saturday 08:00-14:00 or by using the online contact form available on gov.uk.)