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30 July 2021

Child car seat laws in the UK

Find out when you have to use a baby or child car seat, and the penalties you face if you don't and are caught.
Which? Team
Child car seat law

Using a child car seat is a legal requirement in the UK. Rules can be confusing, so we've pulled together everything you need to know so you don't get pulled over and fined.

Find out everything, from UK car seat laws and the differences between height and weight-based child car seats, to whether you can use car seats in an Uber, and the rules for children and car seats in a van.

Check out our top 10 baby car seats, our pick of the best rear-facing toddler car seats, as well as the best car seats for older children to find the best car seat for your little one.

What is the law for child car seats?

UK law states that children must use a child car seat until they're 12 years old or 135cm/4ft 5in tall, whichever comes first.

However, safety experts recommend that you use a child car seat for all children under 150cm/4ft 11in. This is the legal requirement in Ireland and some other European countries, such as Germany and France.

For children weighing more than 36kg (5st 10lb) but under 150cm/4ft 11in, our advice is to go by height. Gov.uk states that children aged 12 or 13 years old, or younger and over 135cm tall, can wear a seatbelt.

Only an EU-approved car seat can be used in the UK. Child car seats approved outside of the EU (the US for example) can't be used in the UK, and EU-approved car seats can't be used in other countries, such as the US.

Buying the wrong child car seat could mean you're putting your child's life at risk, while also breaking the law. 

Which? crash tests every car seat we review. We only recommend the best child car seats - those that do well in crash tests are simple to install and easy to use.

What is the correct child car seat?

An appropriate child car seat is one that:

  • conforms to the United Nations standard, ECE Regulation 44/03 or ECE 44/04 (this is marked on a label on the seat), or is approved under UN R129 (i-Size is a part of R129)
  • is suitable for the child's weight and size, or height (if buying an i-Size seat)
  • is correctly fitted according to the manufacturer's instructions.

Don't get caught out using a booster seat incorrectly. Read our guide: Booster seats, are you breaking the law?

Child car seat law

Height-based or weight-based car seats?

You can choose a child car seat based on your child's weight or height.

Weight-based child car seats:

Most child car seats are split into groups according to the weight of the child they're designed to protect.

These groups are defined by United Nations safety regulations and cover children from birth all the way up to 12 years old or 135cm (around 36kg). 

Moving babies and younger children to the next group before they reach the maximum weight or height for their seat could lead to more severe injuries in a crash. It’s also against the law to put your child in a seat that’s inappropriate.

See our guide to car seat weight groups for more information on what seat to buy and when.

Height-based car seats:

i-Size is part of the European child car seat regulation R129, which came into force in the UK at the beginning of April 2015.

i-Size car seats go by height instead of weight. A true i-Size car seat will only use Isofix connectors, although some baby car seats can still be installed in your car using the car's adult seatbelt. It's mandatory for a baby to be rear-facing in an i-Size seat until he or she is 15 months old.

i-Size car seats will fit all i-Size-certified cars and almost all cars with Isofix. Check with the car manufacturer to see in which position you can use an i-Size car seat in your vehicle.

Find out whether i-Size child car seats are safer and will fit in your car by reading our guide on i-Size car seats.

Child car seat law by age

The rules for vans are the same as for cars.

Child up to three years old

  • Who is responsible? The driver
  • Front seat: Correct child car seat must be used.
  • Rear seat: Children under three must be in a child car seat. If there’s no room for a third child seat in the back of your vehicle, children aged three or under can use the front seat but only if they are in a child car seat. If your vehicle doesn't have seat belts in the back, a child under three can’t travel.

You can’t take children under three on an unexpected journey over a short distance in a vehicle without a seatbelt or the correct child car seat. The only exception to this rule is if it's in a licensed taxi or minicab (private hire vehicles) and the child travels on the rear seats.

See the best baby and child car seats that have come out in top our crash tests.

Child from third birthday up to 135cm in height, or 12th birthday, whichever they reach first

  • Who is responsible? The driver
  • Front seat: Correct child restraint must be used.
  • Rear seat: If there’s no room for a third child seat in the back of your vehicle, children aged three or older can sit in the back using an adult belt.

If your vehicle does not have seatbelts in the rear, a child aged three or older can travel in the back seat without a car seat and without a seatbelt. This rule only applies if the car came without seatbelts in the back originally. A child aged three or over can travel in the rear seat of a licensed taxi or mini cab (private hire vehicle) without a car seat but only if they wear an adult seatbelt. For journeys that are unexpected, necessary and over a short distance, a child aged three or over can sit in the back only, using the adult seatbelt.

Child aged 12-13 years old, or younger and taller than 135cm

  • Who is responsible? The driver
  • Front seat: Seatbelt must be worn.
  • Rear seat: Seatbelt must be worn.

Passengers ages 14 years old and over

  • Who is responsible? The passenger
  • Front seat: Seatbelt must be worn.
  • Rear seat: Seatbelt must be worn.

Children with disabilities or medical conditions

Gov.uk states that the same rules apply for children with disabilities or medical conditions, but they can use a disabled person’s seatbelt or a child restraint designed for their needs.

A doctor can issue an exemption certificate if a child is unable to use a restraint or seatbelt because of their condition.

Dad putting Maxi Cosi infant carrier in car

Do you need a child car seat in a taxi, minicab or Uber?

A driver can be fined up to £500 if a child under 14 isn't in the correct car seat or wearing a seatbelt while you're driving. However, there are exceptions to the law when it comes to travelling in taxis, minicabs and Ubers.

  • children under three can travel without a child’s car seat or seatbelt, but only on a rear seat
  • children aged three or older can travel in a rear seat without a child’s car seat if they wear an adult seatbelt
  • A 2021 survey* by Which? found 54% of parents thought you could be fined if you don't use a car seat for your child in a taxi

If you have a child under three years of age, some experts feel the best option is to sit the child next to you on their own seat (if they are able to), or use your own car seat.

Holding them on your lap isn’t the best option because in the event of a serious crash your body weight may crush the child or, even worse, they may be flung out the car.

We would recommend finding a taxi firm that can provide a car seat for when you travel, or bring your own. 

*Survey carried out in February 2021 of 2,021 parents with a child under the age of five.

Do minibus or coach firms need to provide child car seats?

Minibus or coach drivers and companies don’t have to provide child car seats, so you'll need to bring your own.

On coaches, there is no law requiring children to travel in a child car seat or to use a seat belt, if they're not available.

For minibuses, all children need to travel in rear seats (behind the driver) if a child car seat or adult seat belt is unavailable. Children aged three or older must use a child car seat if there's one available. If there isn't a car seat, they they must use an adult seat belt.

Other exceptions to the child car seat law

No room for a third child seat in the back

If there’s no room for a third child seat in the back seat (where two occupied child car seats in the rear prevent the fitting of a third one) a third child under the age of three can’t travel unless they are in the front seat with the correct child seat.

Children more than three years old can either use the front seat with the correct child seat or sit in the back using an adult belt.

Unexpected but necessary journeys over a short distance

If you have an unexpected but necessary journey over a short distance, and you don't have the correct child car seat, a child over three years old can use the adult seatbelt. 

You must not take children under three in a vehicle without a seatbelt or the correct child car seat (except in the back seat of a taxi or minicab).

Vehicles without seat belts

The following rules only apply if the vehicle was originally made without seatbelts.

Gov.uk states that children under three must be in a child car seat. If there’s no seatbelt, they can’t travel. A child aged three or older can travel in a back seat without a car seat and without a seatbelt if the vehicle doesn’t have one.

Teddy bear in seat belt

Penalties for ignoring the law on using child car seats

The consequences of ignoring the legal requirements could be expensive (at best) or fatal (at worst). Police are able to administer an on-the-spot fine which could be as much as £500 if the case is referred to court.

Remember, the driver of the vehicle is responsible for ensuring all passengers are safely strapped in. If you're the driver, always check. 

Thankfully, it seems parents are becoming increasingly clued up on what you'll be fined for when it comes to transporting children. A 2021 survey* by Which? found 88% of parents know they can be fined if they don't use a car seat for their own young children, while 86% of parents are au fait with the law stating they can be fined for not using a car seat for someone else's young children.

* Survey carried out in February 2021 of 2,021 parents with a child under the age of five.

girl in child car seat

Why can't children just use an adult seatbelt?

Children need their own specially designed child car seat to keep them safe in a crash because their bodies are not simply smaller versions of adult bodies. 

As babies' bodies are in the early stages of development, they need protection based on specific physical traits:

  • Different proportions – babies have bigger heads and smaller limbs
  • Babies' major organs are in different places
  • Babies' bones and muscles aren't fully formed
  • Babies are more vulnerable to injury than adults.

Child car seats are designed to protect a child's most vulnerable areas at each stage of their development.

Restraint systems – adult seatbelts and child car seats – are designed to do three things:

  1. Keep people away from the vehicle structure during a crash
  2. Reduce their momentum in a controlled way
  3. Distribute the forces of a crash over the strongest parts of the body, with minimum damage to the soft tissue and organs.

Children are too small to position the adult belt over their shoulders and pelvis correctly, and their bones aren't strong enough to absorb the energy of a crash without affecting their internal organs.

A proper child-restraint system like a car seat provides the best protection for kids as they change and grow.

carrycot vs baby car seat

Can I use a carrycot instead of a child car seat?

Our experts agree that the safest way to transport babies is in a rearward-facing infant car seat. A good car seat will help protect your baby in both frontal and side impact crashes.

However, car seat carrycots can be a good solution for newborn babies, especially premature babies or those with medical conditions who need to be transported lying completely flat.

In this instance we'd recommend a car seat carrycot with good crash test results.

However, a carrycot will take up a lot of space across the back seat, which may not be practical if you have to transport multiple children. They also tend to be outgrown faster than standard baby car seats.

A pushchair carrycot should never be used in a car, unless it's approved for use as a child car seat.

Discover more tips and advice on finding the best car seats for babies.