• A guide to child car seats

A guide to child car seats

The rules of using a child car seat or booster seat in the UK

Making sure your little ones are safe during any car journey is hugely important. When it comes to hiring a vehicle, you’ll want to have the peace of mind that your child is safely secured and the car seat or booster seat you use meets UK regulations. 

In this guide all about child car seats, we highlight the rules of travelling in a car with children, explain the different types of car seats available, and what size you’ll need. Read on to find out more…    

UK law: Using a child car seat or booster seat

In the UK, children are required by law to use a child car seat until they are 12-years-old or 135 centimetres in height - whichever comes first. Beyond that point, children must wear a seat belt when travelling as a passenger in a vehicle. 

The rules for fitting a child car seat:

  • A child’s car seat should only be used if the car is fitted with a diagonal seat belt, if the car seat is designed for use with a lap-style seat belt, or has ISOFIX anchor points in the vehicle.
  • If a rear-facing baby seat is fitted in the front seat, then the front airbags MUST be deactivated by the driver. 
  • A child’s car seat MUST NOT be fitted to vehicles with side-facing passenger seats.      

What types of car seats are there?

Car seats don’t come as a ‘one size fits all’ solution, so you’ll need to choose a model depending on the age, height and weight of your little one. As such, children’s car seats in the UK fall into one of two main categories:

Height-based child car seats

Also known as ‘i-Size’ seats, height-based car seats are required by law to be rear-facing until a child is at least 15-months old. Children over 15-months old must use a forward-facing car seat suitable to the height of the child. 

Weight-based child car seats

These types of car seats are categorised by a child’s weight which dictates the way in which they are secured within the seat. For use in the UK, weight-based child car seats MUST be EU-approved which is confirmed with a label displaying a capital letter ‘E’ in a circle and marked ‘ECE R44’.  

What are the age groups for car seats?

Weight-based child car seats fall into one of five groups of weight categories that operate in a slightly different manner and are designed for ultimate safety. Our table below explains more:



Type of Seat

0kg to 10kg


A lie-flat (also known as lateral) baby carrier, rear-facing baby carrier or rear-facing baby seat fitted with a harness

0kg to 13kg


A rear-facing baby carrier or a rear-facing baby seat fitted with a harness

9kg to 18kg


A rear-facing or forward-facing baby seat fitted with a harness or safety shield

15kg to 25kg


A rear-facing or forward-facing child car seat, high-backed booster seat or booster cushion using a seat belt, harness or safety shield

22kg to 36kg


A rear-facing or forward-facing child car seat, high-backed booster seat or booster cushion using a seat belt, harness or safety shield

It’s worth being aware that manufacturers now only make children’s car booster cushions for group 3 approval. However, this does not affect existing children’s car booster cushions previously manufactured for group 2 use, so you will still be able to use these. 

What is a Group 123 car seat?

A group 123 car seat is a weight-based children’s car seat that combines the three categories displayed in our table above. These car seats are approved for children weighing at least 9kg and will last until the child is up to 36kg in weight.

Usually these types of combination car seats prove more cost-effective as they are designed to last for a number of years, and can be adapted as the child grows in height and weight.    

When can a child travel without a car seat?

The general rule is that a child must be at least 12-years-old or 135cm tall before they can travel in a vehicle without a car seat, booster seat or booster cushion. It is the law for children under three-years-old to travel in a baby carrier or child seat.  

In some cases, children aged between three to 12-years-old can travel in the back seat of a vehicle without a child seat or seat belt. These reasons include:

  • If the child is travelling with parents or guardians in a taxi or minicab
  • If the child is supervised in a minibus, coach or van
  • If the child needs to travel in an emergency
  • If there is no room in the vehicle for another children’s car seat 

What age can a child sit on the front seat in the UK?

Once a child is 12-years-old or 135cm tall they are legally allowed to sit on the front passenger seat of a vehicle when using a seat belt. Before this, children are required to be secured in the back seat using either a child seat, booster seat or booster cushion. 

What is an ISOFIX fitting?

Recognised as an international standard of car seat fitting system, ISOFIX (International Standards Organisation Fix) is designed to automatically lock a children’s car seat or booster seat in place using a series of fixing points. 

This form of fitting system secures the children’s car seat or booster seat without the need of using a seat belt - although this will still be a requirement with some types of car seat.     

How do I know if my car has ISOFIX?

In 2012 it became a mandatory requirement for all newly manufactured cars with four seats or more to be fitted with ISOFIX anchor points as standard practice. Most cars with a registration plate of ‘61’ onwards will already have ISOFIX connection points in the back seats.   

Hire vehicles which cater for the whole family

Here at Rent Direct, hiring a vehicle for the whole family couldn’t be easier. We are a leading provider of rental cars and rental MPVs no matter what your needs. Our fleet consists of family-sized hatchbacks like the Ford Focus, popular SUVs like the Hyundai Tucson or seven-seater MPVs like the peugeot 5008. 

We can even cater for families of up to nine people thanks to our Ford Tourneo Custom passenger van model which also allows plenty of room for luggage too. If you need to fit a children’s car seat, booster seat or booster cushion, then contact us to discuss your requirements and we’ll be only too happy to help.