For your child to be safe and comfortable in the car, you must have a child seat that can fit into the car. If a child passenger is not in a car seat, you can be fined £60 and lose three points off your license.  Your child can only progress out of a car seat once they've reached 12 years of age or if they've grown to be larger than 135 centimetres tall. As a result, it's a good idea to invest in a car seat when your child arrives that it can be used throughout the years.