Will LED bulbs fail an MOT?

Fitting LED or HID bulbs into an existing halogen headlamp unit fails the test for 'light source and lamp not compatible', a major defect, on vehicles first used on or after 1 April 1986. The rule is about the conversion rather than the technology: a complete replacement headlamp unit that was manufactured with LED or HID light sources is perfectly acceptable and must not be failed for it.

Are tinted rear light lenses an MOT failure?

Anything applied to a lens or light source that obviously reduces intensity or changes the emitted colour is a defect. On a position lamp that is minor, so the car passes with it noted, but it becomes major wherever the result is red light to the front, white light to the rear, or heavily reduced light intensity — which is what a heavily smoked rear lens usually produces.

What colour do car lights have to be to pass an MOT?

Headlamps and front position lamps must be white, predominantly white with a blue tinge, or yellow. Rear position lamps and stop lamps must show a steady red, and rear fog lamps red. Front fog lamps must be white, reversing lamps white to the rear, and direction indicators amber at both ends with no white or red showing.

Why has my car failed for a light that works perfectly?

Because this part of the test is about the light a lamp produces rather than whether it comes on. A lamp can illuminate every time and still be the wrong colour, sit outside its permitted position, or be too dim or too bright for the requirements. That is a different defect from a lamp that failed to operate, and it is recorded separately on the certificate.

How much does it cost to fix a lamp colour or position failure?

Usually very little. Correct E-marked bulbs are £10 to £30 a pair and take ten minutes, and removing tint film is half an hour of labour at £20 to £40. It rises where the lamp unit itself has to be replaced: £25 to £80 for a used rear cluster, £60 to £180 for an aftermarket headlamp, plus £15 to £30 for a headlamp aim check afterwards.

MOT defect file

Lamp of the wrong colour, position or intensity

Last updated 27 July 2026

Quick answer

The lamp works perfectly well — it is simply the wrong colour, sitting in the wrong place, or throwing out more or less light than the rules allow. Aftermarket LED bulbs in headlamps built for filament bulbs, and tinted rear lenses, are the two causes a tester meets most often.

Typical cost: £10–£250
DIY viability: Straightforward

What you might notice

Bulbs that look noticeably whiter or bluer than the ones the car left the factory with, usually fitted as an upgrade
Light scattered up the hedgerows and road signs with no clean cut-off, and oncoming drivers flashing you while you are certainly on dipped beam
Smoked or tinted rear lenses, spray tint or vinyl film, which look darker again once the car is wet or dirty
An indicator flashing white or a washed-out lemon rather than amber, usually a clear lens with an ordinary bulb behind it
Nothing you would notice at all, because every one of these lamps lights up — there is no bulb-out warning for a lamp that is simply wrong

What causes it

LED conversion bulbs fitted into a headlamp reflector designed around a halogen filament, which is the commonest cause by a distance
Tint film, smoke spray or dark aftermarket lenses on rear clusters and indicators
A clear or chrome-topped indicator lens fitted without the amber bulb it needs behind it
Wrong-colour or wrong-rating bulbs fitted in a hurry — a plain bulb in an indicator, a blue-tinted 'xenon look' bulb in a headlamp
A lamp unit from a different model or a different market, which can sit at the wrong height or show the wrong colour to the side
Oxidised, crazed or grimy lenses, which cut the intensity without changing anything else about the lamp

Advisory or failure?

Each lamp has to show the colour, sit in the position and produce the intensity the rules set for that particular lamp, and the grading depends on which lamp is wrong. For headlamps, direction indicators, fog lamps and reversing lamps, emitted colour or position not in accordance with the requirements is a major defect and a failure. For front and rear position lamps, daytime running lamps and end-outline marker lamps the same wording is only a minor defect — unless the lamp shows red light to the front, white light to the rear, or has heavily reduced light intensity, each of which is a major defect. Stop lamps follow that pattern too: position or intensity out of specification is minor, but a stop lamp not showing a steady red light, or with significantly reduced intensity, is major. The colours themselves are fixed. Headlamps must be white, predominantly white with a blue tinge, or yellow, and front position lamps the same; rear position lamps must show a steady red. Direction indicators must be amber front and rear, flashing amber only with no white or red showing. Front fog lamps must be white and rear fog lamps red. Reversing lamps must show white to the rear, and are inspected on vehicles first used from 1 September 2009. Two further rules deal with what has been added to a lamp rather than what it was built with. Anything applied to the lens or the light source that obviously reduces intensity or changes the emitted colour is a defect — minor on a position lamp, major on a headlamp, and major on any lamp where the result is red to the front or white to the rear. And existing halogen headlamp units on vehicles first used on or after 1 April 1986 must not be converted to run high intensity discharge or LED bulbs: where that has been done the headlamp is failed for 'light source and lamp not compatible', which is a major defect. That rule is about the conversion rather than the technology — a complete replacement headlamp unit manufactured with an LED or HID light source must not be failed for it, provided the lamp meets everything else, aim included.

Can you fix it yourself?

Straightforward

Most of this comes undone with your hands rather than tools, and it is far better done before the test than after. Put the original type of bulb back in — the handbook, or the marking moulded into the lamp, will tell you which — and buy an E-marked filament bulb rather than the brightest thing on the shelf. Tint film peels off with a heat gun on a low setting and a plastic blade, followed by a proper adhesive remover rather than a solvent that will craze the lens; sprayed-on tint is far harder and usually means a used cluster from a breaker. Two things are worth being honest about. Fitting LED bulbs into a halogen headlamp is not something you can make acceptable by aiming them more carefully, because the unit is what the rule is about, not the adjustment. And a hazed headlamp lens can be polished back, but if the reflector behind it has gone dull and patchy no amount of work on the outside will restore the beam — that one needs a new unit.

What it costs

Most of the time this is the cheapest failure on the certificate. A pair of correct E-marked headlamp bulbs is £10 to £30 and takes ten minutes; indicator and rear bulbs are a few pounds each. Stripping tint film is your own afternoon, or half an hour of labour at £20 to £40. It gets dearer once the lamp itself has to change: a used rear cluster from a breaker is £25 to £80, an aftermarket headlamp unit £60 to £180 and an original-equipment one considerably more, with half an hour to an hour to fit and a headlamp aim check at £15 to £30 afterwards. The top of the band is a car carrying a complete non-approved lighting kit, where the correct units have to be bought back. One warning about the money already spent: LED conversion bulbs cannot be made compliant in a halogen unit, so that outlay is gone, which is why reputable sellers describe them as being for off-road use.

What happens if you ignore it

These are the defects that quietly put your fault onto somebody else. A headlamp running a light source it was not designed around scatters light where the reflector cannot control it, so it dazzles oncoming drivers and, perversely, usually lights the road less well than the halogen bulb it replaced. A tinted rear lens removes brightness from exactly the signal a following driver needs in rain and spray. Red showing to the front, or white to the rear, makes your car ambiguous about which way it is facing, which is why that particular defect is graded major on every lamp on the vehicle. There is a legal dimension beyond the test as well: using a vehicle with lamps that do not comply is an offence in its own right, and a non-compliant lighting modification gives an insurer a straightforward argument to make after a collision at night.

Common questions

Will LED bulbs fail an MOT?: Fitting LED or HID bulbs into an existing halogen headlamp unit fails the test for 'light source and lamp not compatible', a major defect, on vehicles first used on or after 1 April 1986. The rule is about the conversion rather than the technology: a complete replacement headlamp unit that was manufactured with LED or HID light sources is perfectly acceptable and must not be failed for it.
Are tinted rear light lenses an MOT failure?: Anything applied to a lens or light source that obviously reduces intensity or changes the emitted colour is a defect. On a position lamp that is minor, so the car passes with it noted, but it becomes major wherever the result is red light to the front, white light to the rear, or heavily reduced light intensity — which is what a heavily smoked rear lens usually produces.
What colour do car lights have to be to pass an MOT?: Headlamps and front position lamps must be white, predominantly white with a blue tinge, or yellow. Rear position lamps and stop lamps must show a steady red, and rear fog lamps red. Front fog lamps must be white, reversing lamps white to the rear, and direction indicators amber at both ends with no white or red showing.
Why has my car failed for a light that works perfectly?: Because this part of the test is about the light a lamp produces rather than whether it comes on. A lamp can illuminate every time and still be the wrong colour, sit outside its permitted position, or be too dim or too bright for the requirements. That is a different defect from a lamp that failed to operate, and it is recorded separately on the certificate.
How much does it cost to fix a lamp colour or position failure?: Usually very little. Correct E-marked bulbs are £10 to £30 a pair and take ten minutes, and removing tint film is half an hour of labour at £20 to £40. It rises where the lamp unit itself has to be replaced: £25 to £80 for a used rear cluster, £60 to £180 for an aftermarket headlamp, plus £15 to £30 for a headlamp aim check afterwards.

Cars this happens to most

Of every model with at least 2,000 tests in the DVSA data, these record lamp of the wrong colour, position or intensity on the largest share of their MOTs. Across all of them the typical rate is 0.9% of tests.

Chevrolet Orlando5.6%
191 times in 3,392 tests
Ford Focus C-Max5.2%
550 times in 10,593 tests
Peugeot 4064.7%
114 times in 2,421 tests
Toyota Previa4.6%
177 times in 3,852 tests
Vauxhall Vectra4.5%
989 times in 22,040 tests
Nissan Primera4.1%
103 times in 2,490 tests
Nissan NV2004.1%
1,004 times in 24,703 tests
Citroen Xsara3.9%
757 times in 19,396 tests

A high rate here is a property of the fleet as much as the car: these models skew old, and almost everything fails more with age. It is a reason to check the item on a used example, not proof the model is badly built. Models with fewer than 2,000 tests are left out because a rate drawn from a few hundred cars moves too much to rank.

Pass rates for every make and model

Warning lights behind this

This defect is what a tester writes down. What you see from the driver’s seat is a symbol, and it is worth checking which one, because manufacturers reuse the same shape for more than one system.

This is general guidance, not a diagnosis. The severity DVSA records depends on the specific fault found, so the same item can appear as an advisory on one test and a failure on another. Ask a qualified tester or mechanic to inspect the vehicle.

Has this been recorded on your car?

Check the full MOT history for any UK registration.