A licensed taxi has to be a vehicle with fewer than nine passenger seats.
To operate as a taxi-bus the licensed taxi's owner has to acquire from the Traffic Commissioner a Special Restricted Public Service Vehicle operator licence (under section 12 of the Transport Act 1985). This enables the vehicle to run a registered bus service (as a taxi-bus) at certain times of the day and be used for conventional taxi work at other times.
The Local Services (Operation by Taxis) Regulations 1986 requires the display of a "bus" sign and prohibits the use of an illuminated taxi sign during the vehicle's use as a taxi-bus.
The Travel Concessions (Eligible Services) Order 2002 describes circumstances where a taxi-bus could be considered an eligible service for concessionary travel. It is for the local Travel Concession Authority to determine whether a taxi-bus service meets the requirements which include:
being available to the general public at bus stops;
running to a published timetable; and,
offering transport to and from any stops on the route, with fares payable to the driver and not set at a level which is likely to act as a deterrent to bus users.