When viewing a vehicle you'll see 'Vehicle Check' in the left sidebar.
The vehicle check data is provided by AutoTrader and is where to go to quickly check a vehicle's history and background. You can check details like VIN and engine number, when the tax or MOT are due, the mileage at the last MOT and whether it's an imported or stolen vehicle. Detailed MOT history is provided, and when applicable detailed finance and high risk marker data will also be shown.
By default only the basic vehicle check data is provided, in order to access the full vehicle check you must have an AutoTrader account connected with the relevant Full Vehicle Check product. Alternatively you can enable MotorCheck in Business -> Connect Services -> Vehicle Data to bring even more vehicle data into this section.