Child Car Seat Laws in the UK: Complete Guide 2026

Keeping children safe while travelling by car is every parent's priority. UK law has strict requirements about child car seats, and understanding these rules is essential.

UK Child Car Seat Law: The Basics

In the UK, children must use an appropriate child car seat until they reach 135cm tall or their 12th birthday, whichever comes first.

⚠️ Legal Warning

Breaking child car seat laws can result in a fine of up to £500. Using the wrong seat significantly increases injury risk.

Types of Child Car Seats

By Weight (ECE R44)

Group 0: Birth to 10kg – Rear-facing baby seats
Group 0+: Birth to 13kg – Rear-facing baby seats
Group 1: 9kg to 18kg – Forward or rear-facing seats
Group 2: 15kg to 25kg – Booster seats with high backs
Group 3: 22kg to 36kg – Booster cushions

By Height (i-Size / R129)

The newer i-Size standard uses height rather than weight. i-Size seats require children to be rear-facing until at least 15 months old.

💡 Expert Recommendation

Keep children rear-facing for as long as possible – ideally until age 4. Rear-facing seats provide up to 5 times better protection in frontal collisions.

Choosing the Right Car Seat

Child's weight and height: Must be appropriate for current size
Car compatibility: Not all seats fit all cars
ISOFIX vs seat belt: ISOFIX provides more secure connection
Ease of installation: Poorly fitted seats offer reduced protection
Safety ratings: Look for Which? or European NCAP tested seats

Installing Your Car Seat Correctly

Research suggests up to two-thirds of car seats are incorrectly fitted.

Read both car seat and vehicle manuals
Check the angle for rear-facing seats
Ensure the seat doesn't move more than 2.5cm side to side
Check harness height is level with shoulders
Remove bulky clothing before securing children

Special Situations

Taxis

Children under 3 can travel without a car seat in taxis if unavailable, but must be in the rear. Children 3+ can use adult seat belts in the back.

Rental Cars

Most rental companies offer child seats. You can also bring your own if compatible. See our car rental guide.

When to Stop Using a Car Seat

Children can stop using a car seat at 135cm tall or age 12. Use the 5-step belt test:

Can they sit with back against the seat?
Do knees bend at the seat edge?
Does lap belt sit across hips?
Does shoulder belt cross mid-shoulder?
Can they stay seated properly throughout?

Summary

Children must use car seats until 135cm or age 12
Choose seats based on weight/height and car compatibility
Keep children rear-facing as long as possible
Ensure correct installation – get professional checks
Never use seats involved in accidents