Child car seat laws in the UK

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 correct child car seat?

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?

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

Child car seats in vans

The rules for vans are the same as for cars.

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.

Exceptions to the child car seat law

There are a limited number of exceptions to the law, as we've mentioned in the table above:

Child car seats in taxis, minicabs and Uber

• 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

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.

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.

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.

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.