The Highway Code - Rule 100

The driver MUST ensure that all children under 14 years of age in cars, vans and other goods vehicles wear seat belts or sit in an approved child restraint where required. If a child is under 1.35 metres (approx 4 feet 5 inches) tall, a baby seat, child seat, booster seat or booster cushion MUST be used suitable for the child’s weight and fitted to the manufacturer’s instructions.

For your online Highway code go to

 http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/index.htm