Direct Line magazine

Child car seats and the law

Updated on: 19 January 2022

a father secures his son in a car seat

A child car seat provides essential safety for a child in the event of an accident. This guide will give an overview of child car seats and the law, designed to help you make an informed purchase.

Why do children need child car seats?

A lot of time, money and effort is spent on making cars as safe as they can be, but child car seats provide much-needed additional protection to the developing bodies of babies and children.

  • Children (especially babies) have different proportions, with smaller limbs in relation to head size. An adult seat belt doesn’t fit over the shoulders or pelvis correctly when worn without the appropriate child car seat.
  • Babies have their major organs located in different places.
  • Children have unformed muscles and bones.
  • Young children and babies have a higher vulnerability to injury. 

The correct car seat keeps children and babies away from the vehicle structure during an accident, reduces their momentum, and ensures the force of a crash is distributed towards the strongest parts of the body, avoiding the delicate internal organs. The use of a correctly fitted child car seat can reduce the risk of injury to a child by up to 82% and reduce the risk of death by 28%, when compared to using a regular seat belt.

What’s the law on child car seats in the UK?

It’s the law in the UK that a child must use a child car seat until their 12th birthday or they’re 135cm tall, whichever comes first. A baby must travel rear-facing until 9kg, although experts recommend keeping them rear-facing for as long as possible.

Child car seats in the UK must be EU-approved.

Car seat exemptions

For a child’s safety, an appropriate car seat should be used in all cases, but there are situations where it’s not a legal requirement. Head over to RoSPA’s Child Car Seats website for a complete guide on when you can travel without a car seat.

  • Exactly what applies will depend on your situation and child’s age, but some examples include:
  • Travelling in a taxi or privately hired car
  • Making a short-distance journey which is unexpected or sudden
  • There are already two child restraints in the rear, so a third can’t be fitted
  • The car wasn’t manufactured with seat belts
  • The child has a disability or condition, which makes it unsuitable to use a regular child car seat. A doctor can issue an exemption certificate, or you can buy a seat belt or car seat designed especially for a disabled child.

The different types of child car seats

Child safety seats with cuddly toys

When choosing the right seat for your child, there’s a range of orientation and size categories to consider.

Height-based seats

These are known as i-Size seats and should be rear-facing in your car until your child is 15 months old. Your child’s height must be within the range of the seat’s specification.

i-Size car seats will fit all i-Size-certified cars and most cars with Isofix, but where possible it’s worth checking the child seat in your car before buying.

To make sure the seat you’re using is compliant with regulations, it should have a label including a capital ‘E’ (Europe) and ‘R129’.

Weight-based seats

Weight-based seats should be selected according to your child’s weight. They’re categorised into weight ranges and can be rear or forward-facing.


Car seat

Group 0 (0kg-10kg)

Lie-flat baby carrier, rear-facing baby carrier, or rear-facing baby seat using a harness

Group 0+ (0kg-13kg)

Rear-facing baby carrier and rear-facing baby seat using harness

Group 1 (9kg-18kg)

Rear or forward-facing baby seat using harness or safety shield

Group 2 (15kg-25kg)

Rear or forward-facing child seat using a seat belt, harness, or safety shield

Group 3 (22kg-36kg)

Rear or forward-facing child seat using a seat belt, harness, or safety shield

Source:, accessed October 2021

All weight-based seats approved for use in the UK will have a label showing a capital ‘E’ and ‘ECE R44’.

If you’re caught driving a car where a child isn’t safely secured, you’ll receive a £100 fixed penalty notice on the spot. If the matter goes to court, it could cost you as much as £500.

Rear-facing child car seats

Rear-facing seats are a legal requirement for babies up to 9kg, or until they are 15 months old. It’s recommended you keep your child rear-facing for as long as possible, but be sure to move them into a bigger rear-facing seat when necessary.

A rear-facing child safety seat does a better job of supporting the head, neck and spine of infants and toddlers in a crash, because it distributes the force of the collision over the entire body.

Dennis Durbin, Co-scientific director of the Center for Injury Research and Prevention at The Children’s Hospital of Philadelphia 

If there’s an accident on the road, rear-facing seats will offer a baby or young child protection in four unique ways:

  • It prevents the child’s head moving around, which reduces the chance of neck injury
  • It stops the head hitting hard surfaces after impact
  • Pressure is distributed all over the body
  • A protective shell stops shattered glass harming the infant

Forward-facing child car seats

Forward-facing child car seats remain popular, especially as kids get older, but don’t assume that a baby who’s outgrown its rear-facing baby seat should move into a forward-facing seat.

While the legal requirement is to have a child rear-facing until they’re 9kg, it’s recommended they remain rear-facing for as long as possible.

However, the size of rear-facing seats for older children can make them impractical for many cars.

Booster seats

Booster seats are effectively one step up from a regular child car seat, but aimed at slightly older children. A booster seat raises the height of a child, so they’re correctly positioned, and offers additional support for the head and back.

From February 2017, manufacturers have been restricted from producing backless versions. However, there’s no legal requirement for parents with a backless seat to update their current model for a new one. 

You’d typically start looking at a booster seat when your child’s approaching 15kg and/or has outgrown the current seat. This will be around age four, but age should only be used as a guide. You may wish to look into extended rear-facing seats.

What is Isofix?

Isofix is a standard for securely fitting a child seat to a car by locking connectors on the child seat to Isofix points in the car. This means it’s much easier to fit a child seat correctly, reducing the chance of installation errors which would make the seat unsafe.

Every car built after 2011 includes Isofix points. Just check with your car manufacturer or manual if you’re unsure whether you have this safety feature in your car. You can also check for staple-shaped fittings between the back and bottom of the seat – they’re often labelled, making them easier to find. 

Many Isofix seats also feature a leg support or top tether, designed to help prevent the seat from tipping forward in a crash.

You’ll also see booster seats with Isofix, though these must be used in conjunction with the car’s seat belt to secure the child and seat. 

We hope the information in the guide will help you make an informed decision when buying a car seat for your child.

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