Choosing the right car seat is one of the most important safety decisions you’ll make as a parent or carer. In the UK, the rules around child car seats are based on legal requirements and manufacturer safety standards, but advice from safety experts often goes further to improve protection.

At The Nursery Store, we stock both i-Size (R129) and ECE R44/04 car seats, so it’s important to clearly understand what is law, what is guidance, and what applies to your child.

UK Car Seat Law: The Essentials

Under UK law, children must use a child car seat until they are:

• 12 years old, or 
• 135cm tall,  whichever comes first. 

The seat used must also be suitable for the child’s height or weight and meet approved safety standards.

Approved standards include:

• ECE R44/04 (weight-based standard) 
• ECE R129 (i-Size height-based standard) 

Both are legal to use (unless stated otherwise for specific future updates), but i-Size is the most recent standard.

Rear-Facing Car Seats:

Law vs Guidance What the law says

• Under i-Size (R129) regulation, children must travel rear-facing from birth until at least 15 months old 
• This applies only to i-Size compliant seats 
• There is no legal requirement in the UK for R44/04 seats to be rear-facing until 15 months 

What safety guidance says

Safety experts, including road safety organisations, strongly recommend:

• Keeping children rear-facing for as long as possible within the limits of the seat 
• Many children can remain rear-facing up to 2–4 years old, depending on seat type 

Rear-facing seats offer significantly better protection in frontal collisions by supporting the child’s head, neck and spine.

Rear-Facing Car Seats Explained

Rear-facing seats are designed to absorb impact forces and distribute them more evenly across the seat shell.

Suitable use

• From birth 
• Minimum: 15 months (i-Size law requirement where applicable) 
• Extended use: up to approx. 4 years (depending on seat limits) 

Common seat types

• Group 0+ (R44/04): Birth to 13kg (approx. 12–15 months) 
• Group 0+/1 (R44/04): Can allow extended rear-facing up to 18kg depending on model 
• i-Size infant seats (R129): Height-based, typically up to 83cm–105cm depending on seat 

Forward-Facing Car Seats Explained

Forward-facing seats are suitable once a child has outgrown rear-facing limits.

Legal position

• Permitted once the child meets the minimum height/weight requirements of the seat 
• Must always be appropriate for the child’s size 

Typical usage range

• From around 15 months+ (i-Size minimum transition point) 
• Up to 12 years or 135cm 

Seat groups

• Group 1 (R44/04): 9–18kg (approx. 9 months to 4 years) 
• Group 2/3 (R44/04): 15–36kg (approx. 4 to 12 years), usually high-back booster seats 

R44/04 vs i-Size (R129): What’s the Difference? ECE R44/04 (Weight-based)

• Classified by child weight 
• Uses group categories (0, 0+, 1, 2, 3) 
• Can be installed using seatbelt or ISOFIX (depending on model) 
• Still legal to use 

ECE R129 (i-Size)

• Classified by child height 
• ISOFIX installation only 
• Requires rear-facing travel until at least 15 months 
• Includes stricter side-impact testing 

Both are legal standards, but i-Size is considered the most modern safety regulation. Installation Types Correct installation is essential for safety. ISOFIX

• Connects directly to vehicle anchor points 
• Reduces risk of incorrect installation 
• Available on many R129 and some R44/04 seats 

Seatbelt Installation (R44/04)

• Uses the vehicle’s seatbelt system 
• Requires careful routing following manufacturer instructions 
• Still safe when installed correctly 

360° Swivel Seats

• Rotate towards the door for easier access 
• Available in both R44/04 and R129 ranges 
• Helps reduce strain when placing or removing a child 

Key Safety Takeaways

Law: Children must use a suitable car seat until 12 years or 135cm 

i-Size law: Rear-facing is required until at least 15 months 

R44/04 law: No rear-facing age requirement, but seat group rules still apply 

Guidance: Rear-facing for as long as possible is safest practice 

Final Advice

Choosing the right seat is not just about age. Always consider:

Your child’s height and weight 

The seat standard (R44/04 or i-Size) 

Correct installation method 

Vehicle compatibility 

When used correctly, both R44/04 and i-Size seats can provide safe travel, but proper fit and correct usage are essential. If you’re unsure, it’s always worth seeking fitting advice or contacting our team for guidance.

Disclaimer

This guide is for general information only and should not be taken as legal advice. Always refer to UK Government guidance and your car seat manufacturer’s instructions for the most accurate and up-to-date safety information.