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Tips and advice

Child car seat laws explained

What are the current child seat regulations in the UK? Here we give you a complete rundown on what you need to know

child car seat laws

While pressure from governments and consumers has resulted in a fantastic level of safety in modern car technology, the laws surrounding child car seats can be confusing. In the UK, it is a legal requirement for most babies, toddlers and children to use a car seat when in a car, so it's vital to understand child car seat laws. To bring you up to speed, Carbuyer has put together this guide explaining the current child car seat laws.

Lady putting ISOFIX child seat in carWhat is ISOFIX in a car and how do you use it?

What is the law for child car seats?

In the UK, children must be seated in an appropriate child seat, baby carrier or on a booster seat until the age of 12 years old or they are 135cm/4ft 5in tall, whichever comes first. Following this, it’s recommended that they wear a seatbelt while sitting in one of the vehicle's normal seats. 

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The only exception to these rules is when a child aged three or older is in the car during an emergency, during a short, unexpected and necessary journey, or while riding in a taxi, coach or minibus, when different rules apply.

A car seat should be mounted in the back seats in a rear-facing position whenever possible. Child seats must permanently be fixed into position via a seatbelt with a diagonal strap, a lap belt, or ISOFIX anchor points. You must never fit a child seat to a side-facing chair; if you must use the front passenger seat, the passenger airbag must be turned off.

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It is the responsibility of the driver to ensure that any children in the car are using the correct safety equipment, such as an approved child safety seat, which is correctly fitted to the vehicle according to the manufacturer’s instructions. Failing to adhere to child car seat laws can result in a fine of up to £500 and potentially put a child at risk in an accident. 

There are only two types of legally approved child car seats that can be used in the UK, so it’s important to check any seat you purchase meets one of the following United Nations regulations for use on public roads:

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  1. United Nations standard, ECE Regulation 44/03 or ECE 44/04 (R44)
  2. United Nations R129/iSize

The original UN standard R44 regulations were introduced in the early 1990s. However, all car child seats made after 2018 must comply with the updated and even safer R129 regulations. The revised legislation is commonly referred to as iSize, and any new models on sale today need to meet this standard to be sold and used legally in the UK. If you’re looking to buy a new child car seat, look for the iSize designation to ensure it meets all the current safety laws. However, if you have an older R44 model, it can still be used, just as long as it complied with the appropriate legislation when it was new. 

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The iSize standard was introduced to enable modern child car seats to work in conjunction with the latest safety equipment in vehicles. One of the main differences between iSize and R44 compliant child car seats is that iSize enables babies and toddlers up to 15 months of age to sit in a rear-facing position, rather than the 9-12 month maximum for older rules. Research shows that a rear-facing seat is the safest position for a baby or toddler in the event of an accident, so iSize seats are designed to elongate the age at which children can be protected in a rear-facing position. 

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When buying a child car seat, the model you choose must be designed for your child’s weight, size, height or age. These measurements should be listed on the child seat’s packaging or in the detailed specification.

Height or weight-based car seats?

When buying a child car seat, you should check whether the model is measured by height or weight. Most child car seats, including those that meet R44 specifications, are split into groups according to the weight of the child they are made to protect. These car seats will be divided into the following categories: 

Child’s weight

Group

Seats

0kg to 10kg

0

Lie-flat or ‘lateral’ baby carrier, rear-facing baby carrier, or rear-facing Baby seat using a harness

0kg to 13kg

0+

Rear-facing baby carrier or rear-facing baby seat 

9kg to 18kg

1

Rear- or forward-facing baby seat 

15kg to 25kg

2

Rear- or forward-facing child car seat (high-backed booster seat or booster cushion)

22kg to 36kg

3

Rear- or forward-facing child car seat (high-backed booster seat or booster cushion) 

When purchasing a child seat with these designations, it is essential to measure your child's weight and buy the correct car seat accordingly. 

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On the other hand, iSize, or R129 child car seats are developed according to the child’s height instead of weight. You will usually find the height specifications labelled on the product's packaging or detailed specification, so make sure that you check this information closely before making a purchase. 

It is a legal requirement that children under 15 months are positioned in a rear-facing iSize child seat. Once the child is older than 15 months, most iSize child seats can be converted into front-facing seats, though you will need to ensure that the seat’s specifications are correct for your child’s height.

What about ISOFIX-mounted child seats?

The ISOFIX system enables child seats to be mounted to specially designed anchor points of the vehicle’s body for increased support in the case of an accident. All UK-sold iSize seats feature ISOFIX support, though not all R44 seats do. It’s worth checking the small print to see if a child car seat features ISOFIX support, as this can add an extra level of safety to your child seat. 

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It's also worth bearing in mind that if your car does not feature ISOFIX support, an iSize child seat may not fit correctly. ISOFIX anchoring points became mandatory for cars with four seats or more in November 2012, but appeared in many models before this date. Be sure to check whether the chair you’re looking at matches your vehicle's specifications. 

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The most important factor when deciding on a child seat is that it fits perfectly into your vehicle and is specifically designed for your child’s height or weight. If your car does not feature ISOFIX support, you may need to source an older model that is compatible with your vehicle and your child. However, we wouldn’t recommend buying a second-hand child seat, as you can’t be sure of its history and whether its safety has been compromised due to a previous incident. 

What’s the best advice?

Rear-facing child seats such as the new R129 iSize models offer the best safety when it comes to car seats, so if your car uses ISOFIX support, they will be the best product to keep your children safe. 

Our advice is to check your car’s handbook to find out which seats are supported before you buy a child seat, and always ensure that the seat is designed for the height or weight of your child. Finally, it is vital to ensure that any child seat is correctly fitted to the vehicle to provide the most significant level of safety.

Now you understand the law surrounding child car seats, read our guide on choosing the best toddler car seat

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