Child car seat laws

Child car seat laws are in place in the UK to keep children safe when they travel. They can seem complicated at first as they change depending on the child’s age, weight and height, as well as from vehicle to vehicle. But this guide will help you navigate these rules and make sure you stay legal when travelling with young passengers.

Only EU-approved child car seats can be used in the UK – these are identified by the ‘E’ in a circle on the label. You can choose a car seat based on your child’s height or weight , and they must use one until they’re 12 years old or 135cm tall – whichever comes first.

Height-based car seats must be rear-facing until your child is over 15 months old and forward-facing thereafter. If you choose a weight-based car seat, use this table to work out what type your child needs:

Child's weight Car seat type
Under 9kg Must be a rear-facing baby seat
9kg to 18kg Rear or forward-facing baby seat
15kg to 25kg Rear or forward-facing child seat (booster seat)
Over 22kg Booster cushion

Fitting a car seat

When fitting a child car seat, you must :

  • Only use a child car seat if your car’s seat belt has a diagonal strap – unless the car seat is specifically designed for use with a lap seat belt. Alternatively, new cars now come with Isofix fixing points, enabling car seats to be secured directly to the frame of your car.
  • Deactivate any front airbags before fitting a rear-facing baby seat in a front seat. 
  • Do not fit a child car seat in side-facing seats.

When a car seat is not needed

A child can travel without a car seat in some circumstances:

  • In a taxi – Children under three years old must be in the back and over three years old must wear an adult seatbelt.
  • During unexpected, necessary or short journeys. This only applies to children over three years old (unless it is a taxi or minicab) and over threes must wear an adult seatbelt.
  • No room for a third child seat in back – In this case, if the child is under three, the correct car seat must be fitted in the front. If they are over three, they can sit in the back using an adult belt.
  • Vehicles without seat belts – If the child is under three, they cannot travel in this vehicle. If they are over three, they must travel in the back only.


The fixed penalty for failing to wear a seat belt as a driver or passenger is a £100 fine. If the case is taken to court, you could face a fine of up to £500. Failure to ensure that a child passenger uses an appropriate child car seat or wears a seat belt according to the legal requirements could also affect any car insurance claims you make.

Find further information here on car insurance or speak to one of our RAC advisers on 0330 159 1019* to get a quote.

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