Child car seat laws explained

Baffled by current regulations or need more information on new legislation? Read the complete guide to child car seat laws

By BuyaCar team November 10, 2023

Parents will know that there are few more stressful journeys than taking your newborn child home from hospital. One thing you definitely don’t want to worry about is whether your car seat is safe for your little bundle of joy and properly attached, so it’s not surprising that new mums and dads often want to get advice on child car seat safety.

Currently, every child's car seat on sale in the UK should have undergone simulation testing to determine how safe it is and how much protection it gives to the child sat in it. This regulation is known as i-Size (or ECE R129) and focuses on side impact protection and keeping children facing rearwards for much longer than was previously required.

There are hundreds of different options out there for parents to fret over, so we've put together this in-depth guide to make sure you have all the information you need to find the right car seat for your child in order to keep them safe and sound on the road.

We take the safety of children very seriously here at BuyaCar, so we've also collated the safest cars for children, while details on the Euro NCAP safety test might also be of interest to you.

What to look for in a child car seat

Isofix car seats

Many parents will be familiar with Isofix and those with a car manufactured in or after 2012 will find the familiar anchoring points fitted as standard. In short, compatible Isofix safety seats use metal protruding arms that clamp to anchoring points welded to a vehicle’s passenger seats. Often, the car seat also features a leg that sits on the floor to support it.

It means you no longer need to faff around and fight with a seatbelt every time you want to go out, because the Isofix points are strong and part of the car’s chassis. The car seat itself will have a multi-point seatbelt to keep the child in place. Many Isofix car seats have red tabs that turn green when the seat is correctly installed. Don’t worry if you can still wiggle it about a bit - the car seats are generally designed to do that to take some of the impact out of a crash.

Some vehicles feature an Isofix mounting point on every passenger seat, while others may just offer one, but the system adds an extra layer of security, as the locking arms grab and secure a fixed base rather than the child seat relying solely on a seatbelt for crash protection.

The front passenger airbag will have to be deactivated if you'd like children to travel in the front and it's always best to consult the vehicle's manual if you are unsure how to do this.

Another benefit of Isofix is convenience, as certain seats can be quickly and easily removed from the base with a simple click of a button, meaning snoozing little ones can be transported easily and without the seatbelt faff. You can also get seats that swivel, making it easier to get babies in and out - especially once they start to get a bit heavier.

i-Size car seats

It is best to view the i-Size regulation as a new way of classifying a car seat, because despite the UK government passing the ECE R129 as an official safety certification in 2013, these two regulations are still in a transition period.

This means that if you own an ECE R44 seat, it remains perfectly legal. But if you are in the market for a new child car seat you should look for the i-Size logo, as this will slowly phase out seats with older certification in the coming years.

The key difference between i-Size seats and those tested to the old regulations is that they are classified for suitability based on height, rather than weight and age. They also undergo frontal, rear and side impact tests, whereas R44 seats don't have to be tested for side impacts.

Lastly, i-Size seats affix to the car using an Isofix mount only, which is a much more secure way of anchoring a child seat to a vehicle. This could prove problematic for those driving cars manufactured before 2013, as Isofix wasn't a mandatory safety feature. However, some manufacturers, such as Renault and Hyundai, fitted Isofix points much earlier than that.

ECE child car seats

ECE was a safety standard founded and governed by the United Nations that categorises child car seats into groups that are suitable for children of various age groups.

The ECE R44 legislation, which is slowly being phased out by i-Size, was split up into four distinct categories, covered a wide array of age ranges and weights in order to safely seat as child. The groups were as follows:

  • Group 0: Rear-facing baby seats - babies up to 13kg
  • Group 1: Forward-facing - child seats - toddlers and children from 9-18kg
  • Group 2: Booster seats - children from 15-25kg
  • Group 3: Booster cushions - children over 22kg

You'll typically see the group number clearly located on the product, which should give you an idea of how suitable the seat is. You may still come across child seats rated by ECE R44, but we recommend you steer clear as this is now an out-dated system.

Child car seat laws

There are several laws regulating the implementation of child safety in cars. These laws do tend to change on a fairly regular basis, so they are probably a long way off what you remember from your own childhood. We've listed the key ones here.

  • Where a child is under three years old, the passenger-side airbag must be disabled if you intend to affix your rear-facing child seat in the front passenger seat. Children sat in the rear seats must also use the correct child seat.
  • A child aged from 3-12 years, or under 135cm in height, must use the correct child seat in either the front or back seats where a seatbelt is fitted.
  • Children aged 12+ or over 135cm in height must use an adult seat belt where available in either the front or rear seats.

These are just the basics; you can read more about child car seats laws here.

Child seat car laws for newborns

Infant carriers 0-87cm/0-13kg/0-15months

Current regulations

Current regulation states that new-born babies must travel in a Group 0 seat, which is suitable for children up to 10kg or around 6-9 months. Alternatively, a Group 0+ seat, which covers from birth to 12-15 months or 0-13kg, is also suitable. Finally, i-Size seat will be suitable for children up to 85cm in this age group, although this can vary slightly by manufacturer.

Many of these seats will likely feature a series of cushion inserts, which can be jettisoned as the child grows, ensuring a snug fit in the seat at all times, or be labelled as a 'combination seat', which is designed to grow and expand with a child.

No matter the certification, UK law states that children in this age group must travel in a seat that is rearward facing, although you may find that some of the latest combination seats swivel on their base, meaning children can ride forward facing when they reach a certain age or weight.

It is also possible to purchase a 'combination seat', which is designed to grow with a child. A combination seat for this age group would typically incorporate Group 0+ and Group 1, so would be suitable for new-borns to children four years of age.

Future child seat laws

Currently, a child must remain rearward facing until they are heavy enough to fit into a Group 1 seat, so at around 9 months. But i-Size certification and extended rear facing seats, or seats that are designed to travel rearward facing for longer, advise that children should sit this way until they are at least 15 months.

Because the two regulations are currently running alongside each other, it is perfectly legal for a child to travel forward facing, as long as they are in the correct seat Group 1 seat and weigh over 9kg.

However, if an i-Size seat is being used, a child must travel rearward facing until they are 15-months-old.

Child car seat laws from 15 months

(Group 1: 9-18kg/9months to four years/i-Size 105cm)

Current regulations

Things get a little more complicated as children get older, because current legislation states that they can start to travel in forward facing seats from nine months old but it really should be up to the parents to decide suitability.

However, current law states that a child must correctly fit - or fill - his or her harness and be able to sit unaided for 30 minutes before travelling forward facing.

A child will have typically outgrown their Group 0+ seat at this point, so parents should look out for Group 1 seats that weigh between 9-18kg and are aged from nine months to four years old.

Future regulations

The introduction of i-Size seats will measure a child on their height and weight, meaning these seats will usually be suitable rearward facing from birth until they reach 105cm. This is thanks to clever adjustable headrests and restraints that can be moved as the child grows.

Child car seat laws from 4 to 12 years old

(Group 2,3: 15-36kg / i-Size 100-150cm)

Current regulations

As a child gets older and larger, they will typically out-grow a car seat and will begin to move into a high backed booster seat or a forward-facing child seat that caters for their weight and age. The current legislation states that children must use a seat until they are 12-years-old or 135cm tall, or whichever comes first.

If you have a seat with the latest i-Size certificate, then a seat should fit a child between 100 and 150cm at an approximate age of 3.5 to 12 years old.

Future regulations

Experts believe highback boosters will be recommended for children over 15kg and 105cm tall. Currently, a child can legally use a booster cushion from 15kg, but a new legal proposal would mean they could only be used from 22kg (roughly 9 years old, 125cm).