Under 2026 UK law, there is a specific and somewhat surprising exception for taxis: children under the age of 3 may travel unrestrained on an adult's lap in the rear seat if a correct child car seat is not available. This exception exists for practical reasons, as it is often impossible for taxis to carry every size of child seat. For children aged 3 to 12 (or under 135cm tall), they must use an adult seat belt if a child seat is unavailable. However, safety experts strongly discourage "lap sitting" due to the extreme risks in even low-speed collisions. In 2026, many parents choose to book "licensed private hire" vehicles that offer pre-installed child seats or bring their own portable, "E-marked" travel vests. While it is legal to sit a toddler on your lap in a London Black Cab or a local taxi when no seat is provided, it is always the least safe option and should be treated as a last resort.