Prototypes which are not yet made available for distribution, consumption or use on the GB market do not require UKCA marking. However, the prototype must only be displayed or demonstrated under controlled conditions at trade fairs or exhibitions in GB. This means the product needs to be operated by experts, there must be restricted public contact with the product, the product must not interact inappropriately with other neighbouring products, and it must be clearly indicated on a sign that the product does not meet the GB requirements and will not be made available until it does.
Products undergoing testing or validating pre-production of units do not require UKCA marking. They are still considered to be in the stage of manufacture and therefore have not been placed on the GB market.
However, fully manufactured products intended for consumer testing need to meet the UK requirements as they apply in GB at the time the consumer testing takes place.