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UK car seat regulations explained

Car seat regulations can be confusing, especially with new laws introduced in 2013 and 2017. But it's important to ensure you're informed and up to date before you buy. Here's what you need to know

By Laura Westerman | Last updated Dec 4, 2023

Happy baby in car seat

Car seat legislation explained

UK law states that children under the age of 12 or 1.35m/4ft 4in tall (whichever comes first) travelling in a car or van must use an age-/size-appropriate car seat. What's deemed 'appropriate' changes as your child grows – more on each stage later.

Child car seats must adhere to the appropriate legislation, which includes crash-simulation testing. And remember, it is the driver’s responsibility to check any passengers under the age of 14 are correctly restrained.

There are currently two valid car seat regulations in the UK (and Europe):

ECE R44 / 04 (often referred to as simply, ‘R44’) was introduced in the 1980s and is still valid today. Under R44, you choose a car seat based on the child’s weight with an age guideline. This regulation is labelled with an ‘E’ in a circle and then 'ECE R44', which you'll see on the seat itself.

'i-Size' refers specifically to Phase 1 of E129 introduced in 2013, relating to baby and toddler car seats. The i-Size seats differ from R44 seats as they have an additional side-impact test to assess protection if your vehicle is involved in a collision. It also ensures that children under 15 months travel in the rearward facing position, which is proven to be five times safer than the forward facing position

You can identify an i-size seat as it will have an 'E' in a circle on it. Under R129, you select a car seat based on your child’s height only and the car seat must be installed using an attachment system called Isofix (more on this in a minute). R129 is an evolving regulation, that is it is still being developed by safety experts, car seat manufacturers, car manufacturers and lawmakers, so keep an eye on changes to the law. A second phase of i-size has recently been introduced which is suitable for children between 100 and 135cm in height.

It is expected that R129 will eventually replace R44. But for now, the two run alongside each other (and will do until at least 2018). We'll update this page as and when new information becomes available or changes are made to UK regulations, but basically, if you're buying new you'll want to go for an R129 height-based seat (where the child is rear-facing up to the age of 15 months). If you haven't got Isofix in your car, go for a R44 seat that is secured by the cars belt as it will be cheaper. R129 must be secured by Isofix.

If you're already using an old R44 seat, where the child only had to be rear-facing until they reach the maximum weight for the seat (normally 13kg for a 0+ seat but check the label) you're good to keep using that for now.

The most important thing to remember is that car seats manufactured under either regulation are legal and safe to use as long as they are installed according to the manufacturer’s instructions. R129 car seats are considered to be safer due to the stricter safety standards and more robust crash simulation testing involved but either type is fine for now.

The main issue with R44 is that many parents move their child up to the next stage of car seat before they’re really ready and they aren't then secured as firmly as they should be. Some parents follow the age guideline rather than the weight while others upgrade when their child reaches the minimum weight for the next size up (rather than waiting until they are the maximum weight limit for the stage they are currently in, which is what was originally intended). R129 uses the child’s height only to decide which car seat is the right size for them, helping to reduce the possibility that a parent is using a wrongly sized car seat for their child.

Still confused? Don’t worry, you’re not alone. Check out our comparison below to understand how R129 ensures a higher safer standard than R44 or have a look at RoSPA's guide to child car seats.

Regulations for baby and toddler car seats

Newborn sleeping in car seat

Traditionally, under R44, the various stages of baby and toddler car seats are known as Group 0, Group 0+ and Group 1 for children up to 10kg, 13kg and 18kg respectively. These car seats can be installed using Isofix or the car's standard three-point seat belt to keep the seat in place and babies are strongly recommended to travel rear facing until they are at least nine months old or exceed the car seat manufacturer's weight limit for rearward facing.

Phase one of R129 (also known as i-Size) was introduced in 2013 for toddler and baby car seats, meaning enhanced performance criteria for car seats for children from birth to 105cm (approximately age four) – essentially what was Group 0 and Group 0+ car seats. These include better side-impact protection, an Isofix installation and for babies to be able to travel rear facing until at least 15 months old but preferably older.

Should my baby be in a rear-facing seat?

Many parents hesitate at the idea of keeping a child rear facing until age four. But it's important to remember that the pressure exerted on a child’s spine and neck muscles in the event of a collision are significantly reduced when rear facing. It is particularly important for babies as their heads (even at nine months old, as per R44) are still relatively large and heavy in comparison to their body and strength, meaning they are unable to prevent their head from being thrown forward in the event of a crash if in the forward-facing position. It is recommended children remain rear facing for as long as possible – at least until 15 months and up to the maximum height limit for the seat.

From 2018 (though there's still no date as yet), it is thought that i-Size will become the regulation standard for baby and toddler car seats. New early years car seats purchased from 2018 onward may need to adhere to R129, not R44.

And remember, under both R44 and R129, it is illegal for a child to sit in the front passenger seat in a rear-facing car seat unless the airbag has been disabled. For peace of mind, it is recommended that infants always travel in the rear seats of the car in an appropriate rear-facing car seat.

Young child in car seat

Regulations for child car seats (age 4+) and booster seats

Until 2017, child car seats were known as Group 2 (15kg-25kg, approximately 15 months to six years) or Group 3 (22-36kg, approximately five to twelve years). These included both highback booster seats and backless booster seats (also known as booster cushions). This meant that children weighting a minimum of 15kg could use a backless booster seat with the car’s standard three-point seatbelt. Any new designed booster cushion can only be used if a child is 22kg and taller than 125cm. Some seats are classed as Group 1/2/3 and are suitable for children weighing 9kg-36kg. The child is secured up to 18kg by the seats internal harness, which is then removed.

Highback booster seats provide better protection for your child (particularly their head, neck and back) in the event of a collision, and better belt routing across the shoulder, ensuring your child is more securely kept in place in an accident. They also provide better side-impact protection.

New R44 regulations regarding the sale and use of booster cushions mean that manufacturers are no longer allowed to introduce new models of backless booster seats (booster cushions) for children shorter than 125cm and weighing less than 22kg.

This change does not affect existing models of booster cushions which are classed as a group 2/3 seat and can be used for children 15kg and above. It will only apply to new booster cushions, not ones which are already in use and meet existing safety standards.

Isofix is not required for this age group as part of R44 or R129, but more and more manufacturers are including Isofix connectors on their highback boosters for added peace of mind and increased safety.

If you're using a highback booster, you can continue using this until your child is 135cm (around age 12). Just remember to adjust the headrest and height of the back of the seat as your child grows. If you're not sure, consult the user guide for your highback booster, or check the manufacturer’s website.

Are there any times when my child does not have to use a car seat?

There are a few exceptional situations in which your child does not have to use a child car seat. Outside of those circumstances listed below, it is currently illegal not to use a car seat for your child.

Can you use a taxi with no child car seat?

Children can travel in taxis and minicabs that do not have a child seat. They must, however, travel on a rear seat and, if they are three years or older, use a seat belt. Children who are less than three years of age can travel without a seat belt in the rear, although this is not a safe option

Can you use coaches and minibuses if you don't have a car seat?

Any child who is transported in a minibus should use a child seat if practical. In the front seats, and any exposed seat, they must use a seat belt or an appropriate child car restraint. All passengers in the rear of minibuses that have an unladen weight of 2,540kg or less must wear seat belts or use an appropriate child restraint if one is available. However, minibus operators are not required to provided child restraints, although they can choose to allow parents to provide and fit their own.

Children under three years of age should use an appropriate child restraint.

Children aged from three years up to their 12th birthday, and under 1.35m (approx 4'5") tall, should use an appropriate child restraint if available, or if not available, wear the seat belt

In minibuses over 2,540kg unladen weight, passengers aged 14 years or over must a wear seat belt. Passengers aged three to 13 years are not yet required by law to wear seat belts, although they are strongly advised to wear a seat belt, or to use a child restraint if one is available.

Are you allowed to take a child in a car in an emergency if you don't have a car seat?

For unexpected journeys if an appropriate child car seat is not available, a child over three years of age can use an adult seat belt if the journey is all of the following:

  • Unexpected (the grandparents taking your child to nursery once a month is not unexpected. They need to get a car seat. This is strictly for emergencies and times when there is no choice.)

  • Necessary

  • Over a short distance

This exception does not apply to children under three years old. You cannot take children under three years in a vehicle without a seat belt or the correct child car seat, except in a taxi or minicab, as described above.

Can I put a child in between two car seats in the back?

Under-threes must be in an appropriate seat. If you can't fit three seats across the back of the car, the child should travel in the front seat in a child car seat, properly fitted. Over-threes can legally travel in the middle of the two seats if restrained by an adult seat belt if there is no other option.

  • Remember, it is illegal to travel with more passengers than there are seatbelts in your car.

What is Isofix?

Isofix is a system that allows child car seats to be tethered to metal anchor points, which are attached to a car's chassis. The child car seat just clicks into the Isofix points.

New i-Size infant car seats can only be fitted using Isofix, which is considered the safest way to install a car seat in your car as it minimises the chance of installing it incorrectly.

If you're using an infant carrier car seat, you'll need to purchase a compatible car seat base to be able to install it using Isofix. The base locks onto the Isofix points and then you just click the car seat into the base. However, many baby, toddler and highback booster seats now include Isofix as standard.

Why does Isofix make installation safer?

Traditionally, car seats were held in place using the car’s standard three-point seat belt. Research from Good Egg Safety (one of the UK’s largest in-car safety campaigners) shows that 71% of child car seats are fitted incorrectly. Many parents fail to thread seat belts correctly or effectively around car seats, meaning their child would be at risk in the event of a collision.

Isofix-compatible car seats use retractable teeth to hook into the main frame of your car and many include a green and red light system to help you know if you've installed the seat correctly.

On your rear passenger seats, locate the metal loops between the car's seat back and bottom cushions (often known as the ‘H’ point). Then, following your car seat's user instructions, extend the car seat’s Isofix connectors (the teeth) to the metal loops, listening for the ‘click’ that shows they’re connected. Finally, retract the teeth so the car seat is pulled into position, snug against the car's native seat and locked safely into position. If your car seat uses a support leg, you'll also need to click this into place. If your vehicle has underfloor storage check with the car manufacturer that it is safe to use this type of seat with the vehicle. Alternatively, it may use what's called a top tether, which is a strap that stretches over and connects to another metal loop on the back of the car's rear passenger seat for added security.

Most modern cars are now Isofix compatible. If you’re not sure, check your car’s manual, or look for a tag on your rear passenger seats labelled ‘Isofix’. But don’t forget to check your car seat is compatible with your car. You can do this on most manufacturers' websites.

And if you're not sure about any aspect of child seats you can visit the Royal Society for the Prevention of Accidents' website for more information.