Follow these steps to check the CO2 emissions of a new, unregistered car.

Before you start

You'll need to know:

• The make and model of the new car

First you need to visit the Gov.uk online CO2 emissions checker.

Select 'New Car' from the list and click 'Next'. The website will then ask for details about the car, including the manufacturer, model, the description (what engine option the car has), fuel type, gear box and engine power.

You can narrow down your search precisely by entering information in every box - the drop-down lists will give you relevant options.

If you wish to see the details for more vehicles you can fill in just the first few boxes and leave the rest of the selections on 'All'. The website will show you the details of every new car of that model it has on its database when you click 'Next'.

Follow these steps to check the CO2 emissions of a used car.

Before you start

You'll need to know:

• The make and model of the used car
• The year and month that the car was first registered. You can find this on the log book (V5C), or by entering the registration into this online tool.

First you need to visit the Gov.uk online CO2 emissions checker.

Select 'Used Car' from the list and click 'Next', and the website will ask for the car's month and year of registration.

You can narrow down your search by choosing the fuel and gearbox types, manufacturer and model of the car. The description shows you the engine options that were available for that car, which you can pick from the list to narrow your search further.

By leaving the selections on 'All', the website will show you the details of every car model that it has on the database as registered during that month and year.

When you click 'Next', you will be shown all the cars that match your search, along with their CO2 emissions.

The details that show will be:

• Manufacturer
• Model
• Description
• Gearbox
• Engine size
• Fuel type
• CO2
• Tax band