Guide to... Child seats - When to upgrade your seat
Move up to the next group if the top of your child's head is above the top of the seat.
A child must use a seat until they are at least 135cm tall - if not, you could get a £30 fixed penalty or a fine of up to £500.
If you have been in a crash, you must replace each child seat in the car. They may have been severely weakened in the accident, so you'll be putting your child at risk.