Tell the police
If the vehicle is a danger to the public or causing an obstruction on a road, footpath, or cycle route, phone 101 to report it to the police.
Check if it's taxed
If it's not taxed, or it's not exempt from tax, report the untaxed vehicle to the Driver & Vehicle Licensing Agency (DVLA) on GOV.UK.
Only the DVLA can remove untaxed vehicles. The council cannot remove them unless they are a risk to public health.
Some vehicles are exempt from tax if they are registered as off the road - they have a 'Statutory Off-Road Notification' (SORN). For example, they are not in use, are not in a public place or are a historical vehicle.
You can check if a vehicle is taxed on the GOV.UK website.
You'll need to tell them the vehicle registration number, make, model and colour of the vehicle and the street name, town and postcode where you saw it.
Check with neighbours
Check with your neighbours or local businesses to see if anyone knows who the vehicle belongs to.