Complex sentence: This interest will be noted in the car's history whenever anyone checks it, so you can't sell the car without clearing your finance first and if you default on the payments the finance company may have the legal right to repossess the vehicle.
Split into simpler sentences: This interest will be noted in the car's history whenever anyone checks it, so that the car cannot be sold without clearing the finance first. If the owner defaults on the payments, the finance company may have the legal right to repossess the vehicle.