Children must use a booster seat until they’re 135cm tall or 12 years of age. It’s the law.
Our advice is that they should actually travel in an appropriate restraint until they’re 150cm tall, because adult seatbelts might not fit them properly.
There are different types, and some only suit certain cars, so make sure you get yours checked by a professional.
You need to get the right seat for your child’s weight and height, and check that it’s fitted correctly for every journey.
And remember that child seats are only designed for one impact. Never re-use a seat that’s been in an accident or buy one second hand, even if it looks OK.