Child car seat law and seat checker

GOV.UK states the rule in one sentence: children must normally use a child car seat until they are 12 years old or 135 centimetres tall, whichever comes first. After that point they must wear an adult seat belt where one is fitted. Highway Code rule 100 puts the same height as 1.35 metres, about 4 feet 5 inches, and says a baby seat, child seat, booster seat or booster cushion must be suitable for the child's weight and fitted to the manufacturer's instructions.

The 12th birthday and 135 cm are alternatives, not a pair you have to meet together. A tall 8 year old who has already reached 135 cm may use an adult belt. A shorter 12 year old may also use an adult belt from that birthday even if they are still under 135 cm. Until the first of those two events, the child needs an approved restraint unless a statutory exception applies.

Age on its own does not choose the seat. A 3 year old can still be well inside a rear facing R129 seat, or already in a forward facing group 1 seat, depending on height, weight and the label. The checker above applies the statutory age and height boundary, then lists the ECE R44 weight groups that cover the weight you entered.

You can choose a child car seat based on height or weight. Height-based seats are the R129 seats commonly sold as i-Size. Only an approved height-based seat is legal: the label must show a capital E in a circle and R129, plus the height range and any maximum weight. Weight-based seats are approved to ECE R44. Their label shows a capital E in a circle and ECE R44, plus the group and weight range.

GOV.UK still lists both systems as legal choices in Great Britain. A shop may now stock mostly R129 seats, but an approved R44 seat you already own remains legal if the child still fits its labelled limits and it is fitted as instructed. Do not mix the two systems on the same child at the same time: pick one approved seat, check the label against this child, and follow that seat's instructions.

R44 groups overlap, so more than one group can cover the same weight. Group 0 is 0 kg to 10 kg, group 0+ is 0 kg to 13 kg, group 1 is 9 kg to 18 kg, group 2 is 15 kg to 25 kg and group 3 is 22 kg to 36 kg. A group match is not a substitute for the printed limits on that particular seat.

A height-based R129 seat must be rear facing until the child is over 15 months old. At exactly 15 months the seat must still face the rear. Once the child is older than 15 months, a forward facing child car seat is permitted if that seat's label covers the child's height and any stated maximum weight.

R44 does not copy that 15 month rule word for word. Group 0 and group 0+ seats are rear facing baby carriers or baby seats. Group 1 starts at 9 kg and may be rear or forward facing. A child who is still 15 months or under, but already 9 kg, can legally use a suitable forward facing R44 group 1 seat. That is a weight-based option, not a reason to turn an R129 seat forward early.

Keep the child in the current seat until they outgrow the labelled height or weight. Moving up a stage the moment they can sit up, or because a sibling's seat is free, is how children end up in a seat the label does not cover.

GOV.UK says you must only use a child car seat if the car's seat belt has a diagonal strap, unless the seat is specifically designed for use with a lap belt or is fitted using ISOFIX anchor points. Do not fit a child car seat on a side facing vehicle seat. Deactivate any front airbags before fitting a rear facing baby seat in a front seat.

Highway Code rule 102 adds the everyday checks: children should get in through the door nearest the kerb, restraints must be fitted to the manufacturer's instructions, children must not sit behind the rear seats in an estate or hatchback unless a special child seat has been fitted, child safety door locks should be used, and children should be kept under control.

Read the vehicle handbook as well as the seat booklet. Some front passenger seats, some ISOFIX positions and some airbag combinations are listed as unsuitable. A seat that is legal for the child can still be the wrong seat for that vehicle.

The front seat is legal for a child in the correct restraint, with one hard limit: a rear facing baby seat cannot sit in front of an active frontal airbag. Deactivate that airbag first, and only if the seat and vehicle makers both allow the installation.

If there is no room for a third child car seat in the back, GOV.UK is specific. Children under 3 must still be in a child car seat, so that child must travel in the front with the correct seat. Children aged 3 or older can sit in the back using an adult belt in that situation.

Once the child reaches 135 cm or their 12th birthday, they use an adult belt in the front or the rear where one is fitted. The driver remains responsible until the child turns 14.

The everyday rule is the child seat. The exceptions are narrow and they do not apply to a planned trip in your own car. GOV.UK lists four situations: a licensed taxi or minicab, a minibus, coach or van, an unexpected journey, and no room for another car seat.

In a licensed taxi or minicab, if the driver does not provide the correct child seat, a child under 3 may travel unrestrained in a rear seat. A child aged 3 or older must travel in the rear and wear an adult seat belt. The exception is for the rear only.

Van rules are the same as car rules. Minibus and coach operators do not have to provide child seats. On a coach, children can travel without a child seat or seat belt if they are not available. In a minibus, all children must travel in rear seats if a child seat or adult belt is not fitted; children aged 3 or older must use a child seat if one is available, or an adult belt if child seats are not fitted or are unsuitable.

The unexpected journey exception is for a child aged 3 or older, using an adult belt, and only if the journey is unexpected, necessary and over a short distance. You cannot take a child under 3 on an unexpected journey without the correct seat unless it is a licensed taxi or minicab and the child travels on a rear seat without a belt.

The 135 cm or 12th birthday boundary is the same in Northern Ireland as in Great Britain. nidirect says all children up to 135 cm, or up to 12 years of age, whichever occurs first, must use a suitable child restraint. Approved seats are Regulation 44.04 or Regulation 129. Rear facing baby seats must not be used in a seat protected by a front airbag unless the airbag has been deactivated.

The penalty is not the same. nidirect states a fixed penalty of £60 and three penalty points for not using the right child restraint, with a court maximum of £500. In Great Britain, current Department for Transport material states a £100 fixed penalty and a court maximum of £500, and these offences currently carry no penalty points. A 2026 consultation proposes adding points in Great Britain; that is a proposal, not the present law.

Scotland and Wales use the same Great Britain child seat rules as England. The Highway Code table in rules 99 to 102 applies across Great Britain. Do not treat a local taxi licensing leaflet as a change to the restraint law itself.

GOV.UK says the same rules apply for children with disabilities or medical conditions, but they can use a disabled person's seat belt or a child restraint designed for their needs. A doctor can issue an exemption certificate if a child is unable to use a restraint or seat belt because of their condition. Carry the certificate. An informal note from a parent is not a substitute.

The driver is still the person the law holds responsible for every child under 14, including in a company car, a hire car and a friend's car. If you collect a hire car, ask before you travel whether ISOFIX is fitted, whether a front airbag can be switched off, and whether the operator will supply an approved seat. Many will not. Take your own seat, or book a car that accepts it.

A company car policy does not override GOV.UK. If the pool car has only lap belts in the rear and your seat needs a diagonal strap, that seat cannot go there unless it is designed for a lap belt or uses ISOFIX.

The common failures are a rear facing seat in front of a live airbag, a booster the child has not yet grown into, a seat on a side facing seat, and treating a taxi exception as a rule for the family car. If you realise the airbag is still on, stop, take the child out, deactivate the airbag or move the seat to the rear, then continue.

If the police stop you, the driver is the person they will deal with for a child under 14. In Great Britain that can be a £100 fixed penalty or a court fine of up to £500. In Northern Ireland nidirect publishes £60 and three points, or up to £500 in court. Pay or contest on the process printed on the notice. Do not drive on with the child unrestrained to 'get home first'.

A second-hand seat with no label, a cracked shell, or a history of a crash is not an approved restraint you can prove. Replace it. The law asks for an approved seat, fitted as instructed, that matches this child.

Myth: the child can use the adult belt from their 7th birthday. The legal boundary is 135 cm or 12 years, whichever happens first.

Myth: i-Size replaced R44 last year so old seats are illegal. GOV.UK still lists approved ECE R44 weight-based seats as legal in Great Britain. nidirect says the same for Regulation 44.04 in Northern Ireland.

Myth: a rear facing seat can go in the front if you push the passenger seat right back. Highway Code rule 101 does not offer that option. The frontal airbag must be deactivated.

Myth: the taxi exception lets you leave the seat at home for a planned car journey. It does not. The exception is for a licensed taxi or minicab when the correct seat is not provided, and only in the rear.

Myth: the MOT tester will tell you if the child seat is legal. An MOT does not inspect a child restraint.