Section 4.1.4 of the current MOT inspection manuals for both motorcycles and cars and passenger vehicles states ‘Existing halogen headlamp units should not be converted to be used with high intensity discharge (HID) or light emitting diode (LED) bulbs. If such a conversion has been done, you must fail the headlamp.’
Class 3, 4, 5 and 7 vehicles
For class 3, 4, 5 and 7 vehicles, the defect ‘Light source and lamp not compatible’ only applies to vehicles first used on or after 1 April 1986.
Should a vehicle be presented for an MOT test with conversions before 1 April 1986 they must not be failed with immediate effect.
Vehicles presented with converted halogen headlamp units first used on or after 1 April 1986 will continue to be failed.
Headlamps must comply with all other requirements of the test and headlamp aim.
Source: MOT special notice 01-21: headlamp conversions – GOV.UK