A guide to child car seats

Last Updated: 18 September 2026

Keeping your little ones safe on any car journey is hugely important. When you're hiring a vehicle, you’ll want peace of mind that your child is safely secured and that the car seat or booster seat 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. After that, 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, the driver MUST deactivate the front airbags. 
• 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 based on your little one's age, height, and weight. 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 must use a forward-facing car seat suitable to the child's height. 

Weight-based child car seats

These car seats are categorised by a child’s weight, which dictates how they are secured in the seat. For use in the UK, weight-based child car seats MUST be EU-approved, as shown by 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 weight groups that operate slightly differently and are designed for maximum safety. Our table below explains more:

Be 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 can still 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 weighs up to 36kg.

Usually, these types of combination car seats are more cost-effective because 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. Children under three years old must travel in a baby carrier or child seat.  

In some cases, children aged between three and 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 child’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 can legally sit in the front passenger seat of a vehicle when using a seat belt. Before then, children must be secured in the back seat using 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 child’s car seat or booster seat in place using a series of fixing points. 

This fitting system secures the child’s car seat or booster seat without using a seat belt, although some car seats still require one.     

How do I know if my car has ISOFIX?

In 2012, it became mandatory for all newly manufactured cars with four seats or more to be fitted with ISOFIX anchor points as standard. 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 includes family-sized hatchbacks like the Ford Focus, popular SUVs like the Hyundai Tucson, and seven-seater MPVs like the Peugeot 5008. 

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