Car child seat laws: everything you need to know

Child seats are a legal requirement in the UK but road safety laws have been updated over the years and understanding the latest rules can be confusing.

By law, all children must use a child car seat until they’re 12 years old or 135 centimetres tall, whichever comes first. You risk a £500 fine if you’re caught using an unsuitable or incorrectly fitted car seat. The rules for cars are the same as for vans.

That's why it's important that you take time to select the right child seat. Not only will it give your little one the best possible protection in the event of a crash, but it will also ensure they are comfortable on short and long trips.

Read the RAC's guide to ensure you keep your child safe and stay on the right side of the law.

UK laws on using child car seats

UK law dictates that a child must use a child car seat until they’re 12-years-old or 135cm tall, whichever comes first. Children over the age of 12 or more than 135cm tall must wear a seat belt.

Since March 2017, all new-to-market backless booster seats are only approved for children weighing more than 22kg or taller than 125cm.

Previously, children who weighed as little as 15kg could use backless booster seats, but concerns over safety resulted in a change in the law.

Only seats approved by the EU are legal in the UK: these will have a label with a capital ‘E’ in a circle and ‘ECE R44’.

What is the best child seat?

The best child seat must meet the following criteria:

• Be suitable for your child's size and weight
• Be fitted correctly, as detailed in the seat manufacturer's instructions

• Meets the United Nations standard, ECE Regulation 44.04 (or Regulation 44.03) or i-size regulation R129 (usually marked on a label or sticker on the seat)

What car seat should my child use and when?

You can choose a car seat for your child based either on the child’s height or weight.

• Height-based child seats are called i-Size seats
• Weight-based child seats offer a range of options: 0kg to 10kg or 13kg, 9kg to 18kg, 15kg to 25kg, and 22kg to 36kg

Travelling rear-facing offers the best protection for toddlers and babies. If you use an i-Size child seat, the child must be rear-facing seat until they are 15 months old.

Never fit a rear-facing child seat in the front of a vehicle if there is an active airbag on the passenger side of the car. If the airbag deploys it will strike the seat and may cause serious injury to the child.

Children weighing more than 22kg or taller than 125cm can use a backless booster seat.

Children of 12 years old or taller than 135cm do not need to use a child seat. Before this age or height they must do by law.

Child seats must be fitted either using Isofix mountings or a diagonal seat belt strap. 

For smaller children, a highback booster seat is recommended.

Weight-based car seat sizes

Weight-based car seats are divided into 3 main groups, depending on your baby or child's age and weight. Approved weight-based seats will have a label showing a capital ‘E’ in a circle and ‘ECE R44’.

Height-based car seats?

Introduced in 2013, ‘i-size’ (R129) car seats were created to improve protection from side impacts and make car seats easier to fit. These child seats will have a label showing a capital ‘E’ in a circle and ‘R129’.

Unlike weight-based car seats, i-size are height-based and only use Isofix connectors (although some can be fitted using the car’s seatbelt).

Many cars are i-size certified, but some are limited to which positions and seats they can fit. If in doubt, contact the manufacturer of your child seat.

When can children legally travel without a car seat?

There are some exceptions when a child does not need to legally use a car seat:

• If the vehicle doesn't have seat belts: A child aged three or more can travel in a back seat without a child car seat or belt

• Taxi or minicab: A child can travel without a car seat, but wearing a seat belt, if the driver doesn’t provide the correct child car seat. They must travel in the rear and wear an adult seat belt if they’re over the age of three. Children under three should travel without a seat belt
• Coach or minibus: A child can travel without a car seat, but must travel in the rear seats of the minibus if a child car seat or an adult seat belt isn’t fitted. If child car seats are not fitted or deemed unsuitable, children aged three or older travelling in a minibus must use a seat belt
• Unexpected but necessary journey: A child aged three or older may use an adult seat belt if making an unexpected but necessary journey over a short distance, for example

The same rules apply for children with disabilities or medical conditions, but they may use a disabled person’s seat belt or child restraint designed for their needs. A doctor may issue an exemption certificate if necessary.

If your car doesn't have space for a third child car seat in the back, the child must travel in the front seat with the correct child car seat.

However, if you don’t make sure any child passengers have the right car seat, in accordance with the law, and they’re injured or killed in an accident, your car insurance may not cover you. Even if that is temporary car insurance. 

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What is a booster seat?

Booster seats, as their name suggests, raises your child’s body so they can be suitably secured by a standard, adult seatbelt.

There are two types of booster seat available in the UK:

• Backless booster seats: These do not have a back or headrest to position your child within the car seat and belt
• High-back booster seats: A high-back booster seat has a headrest and back that offers additional support for your child’s head and neck. These are widely considered to be the best booster seat for comfort and safety

What are the laws for booster seats in the UK?

You can legally use a booster seat in the UK, but the rules vary depending on the age of the seat and the weight of your child.

The laws for using a booster seat in the UK are:

• Children must use a child car seat or suitable booster seat until they’re 12 years old or 135 centimetres tall, whichever comes first
• A backless booster seat should only be used by children who are taller than 125cm and weighing more than 22kg
• High-back booster seats can be used by children who weigh between 15-36kg

Older backless booster seats (manufactured before March 2017) can still legally be used by a child weighing 15-36kg but this is not recommended by child seat experts.

What to look for when buying a child car seat

The easiest way to make sure your child is protected (and that you avoid unintentionally breaking the law) is to look for a brand new ‘i-size’ car seat based on the child’s height.

All i-size car seats come with Isofix fitting points. This means you can fit the car seat to your car safely without relying on seat-belts. Isofix fitting points are fitted to new cars as standard.

With so many car seats on sale, it can be very confusing choosing the right one for your child. We’d suggest buying one from a high street store. RAC Shop also stocks car seats.

Secondhand seats are often cheap - but you don’t know their history and whether they’ve been involved in a crash which might have damaged them.

All car seats used in the UK must be European-approved. Look out for a label showing a capital ‘E’ in a circle - this indicates that it complies with the latest regulations.

Safety and car seats - the facts

It wasn’t until the 1960s that any real thought was given to child seats – and even then, they were simple booster seats designed to give children a better view out of windows than to keep them safe in the event of a crash.

Volvo has a reputation for being the first with safety advances, so it’s no surprise that it launched a child seat prototype in 1964.

Inspired by how astronauts travel backwards, medical doctor Bertil Aldman (subsequently professor in traffic safety at Chalmers University of Technology), developed the very first child seat prototype and tested it in a Volvo PV544.

The Volvo Amazon was available with a front passenger’s seat that could be turned around entirely from 1967, allowing a child to be kept in place using straps and a padded backrest.

The firm launched the world’s first booster cushion in 1976, and in 1990 the Volvo 960 was launched with an integrated booster cushion.

Seat-belts didn’t become a legal requirement for rear-seat passengers in the UK until 1987 and, remarkably, laws requiring children to use special car seats weren’t introduced until 2006!

How to fit Isofix child seat

It’s important to note that not all Isofix child seats are approved for all makes and models of car and van. Check compatibility before you buy (some child seat manufacturers have have online guides showing which cars their seats will fit in).

• Read the child seat instructions: The manufacturer will detail how the seat works and fits in to the vehicle. It'll also identify specific features (such as tilt and rotate functions)
• locate the Isofix anchor points in your vehicle: These are found in the gap between the rear seat cushion and backrest. They may be located behind a plastic cover or embedded within the seat (accessible via small zip). Some vehicles will have a third Isofix anchor point for anchor point for a top tether (usually on the ceiling, on the rear seat back or boot floor)
• Open the car door to its maximum point (usually 90 degrees): This will give you plenty of room to load the child seat into the car without damaging the vehicle or the child seat
• Place the child seat on the rear seat of the car and slide the Isofix connectors into the anchor points: There will be an audible click when the connection has been successfully made. There may also be a visible marker on the child seat (which turns red to green) when the seat has been safely attached

If using a top tether, connect the strap to the tether point in the car. Never attached the strap to anything else within the car (such as parcel shelf or head rest)

If the child seat has a supporting leg, make sure it is correctly placed against the floor. Again, there may be an audible click and a visible market which turns from red to green.

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When you are roadtripping abroad, ensure you get European Breakdown cover.

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Are you looking for a car seat for your little one? Browse our range of child car seats, over to the RAC Shop.