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Booster seat and child car seat laws

UK's car seat laws require you to fit a booster seat if your child is below 12. Make sure you buy the right booster seat first time.

If you’re driving with a child under the age of 12 and 135 cm (4'5") in height, you’re legally required to fit a child car seat or a booster seat for the child’s safety.
It’s important that you choose the right seat for your child. Picking the wrong car seat could put your child at risk of getting hurt. So, before you buy a child seat, here’s what you need to know: 1. You need to choose a seat for your child depending on their weight or height – it doesn’t matter how old your child is. 2. Seats can be rear-facing or front-facing – again, this will depend on your child’s weight or height. 3. You can only use EU-approved standard car seats in the UK. You can check if the booster seat meets the safety standards or not by checking the label. Look for a capital ‘E’ in a circle and ‘ECE R44’ if it’s a weight-based seat or ‘R129’ if it’s a height-based seat. 4. Always deactivate the airbags when carrying your child in a rear-facing seat in the front. Otherwise, you should place the rear-facing child seat in the rear. Keep reading to learn which car seat you’ll need for your child, the difference between isofix and isofit, and how to fit the best car seat for your child.

Car seat groups

Child seats come in various shapes and sizes for children of different heights and weights.
Kids’ car seats are usually divided into ‘baby or infant seats’, ‘toddler seats’ and ‘booster or child seats’. The terms used for different size seats can vary according to the different brands, so make sure you check the size guide first with the seller.

Weight-based child seats


Baby car seat

The two main car seats for babies are: 1. an infant carrier – which can come with or without a base 2. a larger fixed seat style Infant carriers are convenient as the base always stays secured in the car, but they can be expensive. A fixed seat may cost the same as an infant carrier, but it usually offers better value as it can be used up to a much higher age. However, a fixed seat can be inconvenient if you’re in and out of the car a lot. Rear-facing seats provide better protection for your baby’s head, neck and spine than a forward-facing seat. Thus, it is recommended you keep children in a rear-facing seat for as long as possible. Also, NHS recommends buying a baby seat before the birth of your baby as you’ll need it to drive your newborn home from the place of birth. This way, you can practice fitting the seat beforehand. Rear-facing seats provide better protection for your baby’s head, neck and spine than a forward-facing seat. Thus, it is recommended you keep children in a rear-facing seat for as long as possible. Also, NHS recommends buying a baby seat before the birth of your baby as you’ll need it to drive your newborn home from the place of birth. This way, you can practice fitting the seat beforehand.

Baby car seat: car size groups

Baby seats come under three car seat groups: • Group 0 for newborns weighing a maximum 10 kg • Group 0+ for babies up to 13 kg (equates to between 12 and 15 months roughly) • Group 1 for babies between 9 – 18 kg (about nine months to four years roughly) All baby seats in group 0 and group 0+ are rear-facing.

Toddler car seat

When your baby stops being a baby, they’ll need to graduate to a toddler seat. Majority of car seat sellers refer to a group 0+/1 combination seat as a toddler seat but some may refer to these as a baby seat, so make sure you check the size guide first.

Toddler seat: car size groups

A combination group 0+ and 1 seat is suitable for a child of up to 18 kg (or about four years old). Toddler seats may appear to take up more space in the car, but if you can fit an infant carrier on a base, then usually most combination seats will take up no more room. However, access can be restricted in some cars, so a rotating seat can make it much easier to load and unload the little one.

Booster seat

Booster seats are meant for children between 15-36 kgs. Booster seats lift your child to an adult’s height so that they can use the car’s seat belt. They are also known as simply ‘car child seats’. This is the final stage before your child can use the car’s seat belt without using a car seat. If your child is above 22 kgs weight, or 125 cm tall, you can use a ‘booster cushion’ which is basically a backless booster seat, so it doesn’t offer side impact protection. You can buy booster seats with a removable back, but it’s usually advised to keep the back in place – especially if it incorporates side wings – as it gives valuable extra protection.

Booster seat: car size groups

Booster seats come under group 2-3 car seats. Group 2 car seats are for children between 15-25 kgs, whereas group 3 car seats cover children weighing 22-36 kgs. There’s also a wide variety of combination seats such as a group 2/3 seat, which makes it suitable for children between 15-36 kgs. This can be cheaper as you won’t need to buy two separate child seats, but it may not offer the same level of protection. Car seats in group 2 and 3 can be either front or rear-facing, and use the car’s seat belt, a harness or a safety shield.

Height-based child seats

Height-based seats, also known as ‘i-Size’ seats, were introduced in the UK in 2013 as they’re easy to use and provide a higher level of protection. These car seats are based on your child’s height rather than their weight, so you need to make sure the car seat’s suitable for your child’s height. All i-Size seats are rear-facing until your child is over 15 months old. You could continue using a rear-faced seat or switch to a front-facing seat after your child is over 15 months of age. You’ll usually find three groups of height-based seats: • Birth to 85 cm • Birth to 105 cm (up to 15 months roughly) • 100 – 135 cm or sometimes 135 – 150 cm (four years - 11 years roughly) Again, this can vary for different sellers so make sure you check the size guide.

Benefits of a height-based car seat

• Parents usually know their child’s height better than their weight and can judge changes in height better • i-Size seats keep your child in a rearward-facing seat for longer (up to 15 months old minimum) which is safer and provides better protection than a forward-facing seat • i-Size seats go through a more rigorous safety test to ensure your child’s protected on all sides in case of an accident • i-Size seats are Isofix compatible which makes them easier to install

Isofix car seat

Isofix is an international standard for fixing child car seats in your car using a pair of metal mounts that are pre-attached to the car seat’s frame. Isofix is an alternative to using the car’s seat belts. Isofix makes it easy to secure the child seat - you simply need to click the clips on the child seat to the Isofix mounts and the foot prop that rests on the floor of the car. The car may have a Top Tether (a strap that attaches to a dedicated mount) usually on the back of the car’s seat instead of the foot prop. Most Isofix have an indicator on the seat which turns from red to green to indicate the child seat’s been installed properly. In theory, it’s a universal system, but not every Isofix seat will fit every set of Isofix mounts. Before you buy a new seat, you should check it is compatible with your car, which you can do by contacting the maker of the seat.

How does Isofix differ from Isofit?

Isofit applies to larger seats than Isofix – groups 2 and 3, rather than groups 0, 0+ and 1 – and, while the seat is attached to the car using the same mounts, the difference is that the child is secured using the car’s seat belts, rather than a harness built into the child seat.

Booster seats FAQs

How do you fit a child car seat?


To ensure you fit the child car seat properly, make sure you read and follow the instruction manual, as seat installation varies. If your booster seat is Isofix compatible, you simply need to secure the seat in the fittings and check that it’s installed properly, either by looking at an indicator on the seat or listening out for a tell-tale click. Make sure you remove any of the car’s head restraints that are in the way. When you’re fitting the seat with the car’s belts, feed all the slack out of the belt. To make sure everything is still nice and tight, simply check the lap belt section is tight enough to flick when loading the little one in daily. As a guide, you should only be able to fit a couple of fingers between your child’s chest and the straps. Remember to adjust the straps every trip, as the clothes your child wears will affect how tightly the belts fit. A good routine to get into is to lengthen the harness as you get your child out so that it’s ready to suit whatever clothing your little one is wearing when you return to the car. It’s best to fit any booster seat in the rear seat, preferably in the centre. And, most importantly, only use the front seat if the passenger airbag is not active. Make sure any adjustable parts on the seat, like a backrest or headrest, are positioned correctly for your child.

When can a child sit without a booster seat in the UK?

The law says that children must use a car seat until they’re 12 years old or 135 cm tall, whichever is sooner. However, RoSPA’s (the Royal Society for the Prevention of Accidents) advice is to wait until they are 150 cm (5ft) or taller before moving them to the seat belt on their own. As with any child seat, you should only stop using it when your child has outgrown it.

More tips on using a child car seat:

• Remember to fasten the booster seat even when nobody is sitting on it or remove it from the car altogether. An unfixed booster cushion is a loose projectile if you have an accident, and the last thing you want is a loose ‘safety device’ injuring you.
• Don’t be in any rush to have a forward-facing car seat for babies - only use it if your child is too heavy or too tall for a rear-facing seat. Your child can see plenty facing backwards, and mirrors are available, so they can see you and you can check on them, too. Need a new car for you and your family? Here are our picks of the best family cars and the safest cars to help you choose the best car.

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