Lights are the single biggest source of MOT defects in Britain, on cars, on vans and on motorcycles. They are also, on a car, almost never dangerous and almost always cheap. This guide covers cars and light vans in classes 3 and 4, goods vehicles in class 7, and motorcycles in classes 1 and 2. In summary:
DVSA publishes MOT results by defect category every three months. The full 2025 to 2026 year for class 3 and 4 vehicles, meaning cars and light vans up to 3,000kg, was published on 10 September 2026. The lamps row reads like this.
| Measure | Lamps and electrical | For comparison |
|---|---|---|
| Share of all tests with at least one defect in this category | 10.44 percent | Suspension 8.90, brakes 6.10, tyres 6.23 |
| Share of all defects recorded | 24.89 percent | Suspension 20.49, brakes 15.18, tyres 12.94 |
| Share of all Major defects | 29.18 percent | Suspension 23.25, brakes 12.71 |
| Share of all Dangerous defects | 1.27 percent | Tyres 60.60, brakes 28.80 |
The overall initial failure rate for cars and light vans that year was 27.51 percent on 33,310,534 initial tests. Apply the 10.44 percent figure and roughly 3.5 million cars and vans picked up a lamps defect in twelve months.
The pattern is stable rather than a one year oddity. In April to June 2026, lamps were 9.98 percent of tests and 24.67 percent of defects, still the largest category. There is a mild autumn rise, 10.87 percent of tests in October to December 2025 against 10.36 percent in April to June 2025, with the same shape the year before. That is about half a percentage point, not the dramatic winter spike often claimed.
Section 4 of the DVSA inspection manual covers lamps, reflectors and electrical equipment. Every defect carries a reference number, and that reference is what ends up on the certificate and in the MOT record. These are the lines that come up most.
| Manual reference | Defect | Category |
|---|---|---|
| 4.1.1 (a)(ii) | Headlamp missing or inoperative, or more than half the LED sources out | Major |
| 4.1.1 (a)(i) | Up to half the LED sources in a headlamp not working | Minor |
| 4.1.2 (a) | Headlamp aim not within the limits in the requirements | Major |
| 4.1.2 (b) | Headlamp aim unable to be tested | Major |
| 4.1.4 (c) | Light source and lamp not compatible | Major |
| 4.3.1 (a)(ii) | A stop lamp missing or inoperative | Major |
| 4.3.1 (a)(iii) | All stop lamps missing or inoperative | Dangerous |
| 4.4.1 (a)(ii) | A direction indicator missing or inoperative | Major |
| 4.4.4 (a) | Indicator flash rate not between 60 and 120 times a minute | Minor |
| 4.5.1 (a)(ii) | Obligatory rear fog lamp missing, or a fog lamp inoperative | Major |
| 4.6.1 (a) | Reversing lamp inoperative, vehicles first used from 1 September 2009 | Major |
| 4.7.1 (b)(i) | One registration plate lamp out where two or more are fitted | Minor |
| 4.7.1 (b)(ii) | The only registration plate lamp out, or all of them out | Major |
| 4.8.1 (a)(ii) | Reflector damaged over more than half its reflecting surface | Major |
| 4.9.1 (a)(ii) | Main beam or rear fog tell-tale missing or inoperative | Major |
Five rules in that section are worth knowing because garages rarely quote them.
Everything above is a bulb, a lens or a connector. Aim is different, and it is the part of section 4 that costs real money.
The tester puts the vehicle on a marked standing area, lines up beam setting equipment and reads the cut-off against a grid. For a European type dipped beam, the cut-off must sit between the 0.5 percent and 2.75 percent horizontal lines where the headlamp centre is 850mm or less from the ground, and between 1.25 percent and 2.75 percent where it is higher. The kick up to the left must be visible unless it has been masked or the lamp has a flat top pattern.
Two practical points come out of the manual. First, the tester must not carry out repairs during a test but is expressly allowed to make minor adjustments to headlamp aim, so on many cars this is a screwdriver turn at the bay and no fail at all. It pays to ask rather than assume. Second, where driver adjustable beam controls are fitted, the aim is checked at whatever setting the car arrived in, and only re-checked at the highest setting if it would otherwise fail for being too low. A dash dial left on 3 after a loaded trip can put a healthy headlamp outside the band.
Aim also fails when it cannot be measured. Reference 4.1.2 (b), "headlamp aim unable to be tested", is a Major, and a badly clouded lens or a scattered beam pattern from the wrong bulb lands there.
Manual reference 4.1.4 is blunt about this. Existing halogen headlamp units on vehicles first used on or after 1 April 1986 must not be converted to use high intensity discharge or LED bulbs. If that conversion has been done, the headlamp must be failed for light source and lamp not compatible, a Major.
The distinction is unit versus bulb. A complete replacement headlamp unit manufactured with LED or HID light sources is fine and must not be failed on that reference, though it still has to meet everything else in section 4. Screwing an LED bulb into a reflector designed for a halogen filament is what fails, and it fails on the rule, not on how bright it looks. A bright white beam on a fifteen year old hatchback is usually a retrofit kit, and the MOT record will show it. The motorcycle manual carries no equivalent rule, which we covered in the guide on motorcycle exhaust and lighting modifications.
A bulb is the cheapest repair in the MOT. Bumper's headlight bulb cost guide, updated 19 September 2025, puts a halogen bulb at as little as £3 over the counter and £15 to £100 fitted, the spread depending almost entirely on how buried the lamp unit is, and reports Halfords charging roughly £8 to £15 for fitting, often free when the bulb is bought there.
| Job | Typical 2026 cost | Note |
|---|---|---|
| Halogen bulb, over the counter | £5 to £30 | £3 at the bottom end for a basic H7 |
| Halogen bulb bought and fitted | £15 to £100 | Bumper range across all cars |
| Fitting labour, accessible unit | £12 to £50 | 15 to 30 minutes at £50 to £100 an hour |
| Fitting labour, bumper off job | £25 to £67 | 30 to 40 minutes or more |
| Xenon or HID bulb | £20 to £100 | High voltage, not a driveway job |
| LED bulb or module | £10 to £150 | Only legal in a unit built for it |
| Ford Fiesta, typical | £16 to £28 | Bumper make and model estimates |
| Volkswagen Golf, typical | £18 to £32 | |
| BMW 3 Series, typical | £16 to £24 | |
| Mercedes-Benz C-Class, typical | £20 to £32 |
Set that against the test itself. The legal maximum MOT fee is £54.85 for a car, £58.60 for a class 7 goods vehicle between 3,000kg and 3,500kg, and £29.65 for a standard motorcycle. A bulb fail followed by a paid full retest costs more in retest fee than in parts, which is exactly why the retest rule below is the thing to get right.
GOV.UK lists the items that get a free partial retest if you take the vehicle away and bring it back to the same test station before the end of the next working day. The list includes lamps, rear reflectors, electrical wiring, registration plates, the main beam tell-tale, and headlamp cleaning or levelling devices that do not need an aim check.
The wording on the lamps entry is "lamps (excluding headlamp aim)". That exclusion is the whole game. Fix a blown bulb overnight, return the next working day, and the retest is free. Fail on aim and you are into a partial retest fee within ten working days, or a full fee after that. Leaving the vehicle at the station for repair and having it retested within ten working days is free in every case, which for an aim adjustment is often the cheaper route even allowing for the labour. The same logic runs through the guides on brake failure costs and tyre failure costs, where brakes are not on the free list and tyres are.
For class 7 goods vehicles between 3,000kg and 3,500kg, lamps are worse on every measure: 17.63 percent of the 1,107,819 tests in 2025 to 2026, 30.58 percent of all defects and 34.26 percent of Major defects, against an overall failure rate of 34.00 percent. Roughly one van in six failed something in section 4. Vans that spend their lives reversing into loading bays lose rear lamp units and reversing lamps at a rate cars do not, and end outline marker lamps are mandatory on vehicles first used on or after 1 April 1991 that are wider than 2,100mm, a rule most van owners have never heard of.
Motorcycles invert the picture. On 1,019,745 class 1 and 2 tests, lamps and reflectors were 7.31 percent of tests, lower than cars, but 40.74 percent of all motorcycle defects and 46.62 percent of Major ones. Most strikingly, lamps were 19.43 percent of all Dangerous motorcycle defects against 1.27 percent on a car. The reason is arithmetic: most bikes have one headlamp and one brake light, so a failure that leaves a car with a spare leaves a bike with nothing. Our guide on the motorcycle MOT covers the class 1 and 2 numbers in full.
Because lamps are a quarter of all defects, almost every car with a few years of history has one somewhere, which makes the line close to worthless as a signal on its own. Do not discount a car because it once failed on a brake light. Four patterns do carry information.
Every one of those lines sits in the free DVSA record with its manual reference, and you can read the whole trail for any UK registration on the MOT Check UK home page. Advisories are a separate skill, covered in what MOT advisories actually mean.
Lights are the most common thing wrong with a British vehicle at its MOT and, on a car, one of the least serious: a quarter of all recorded defects and barely one percent of the dangerous ones. If your car fails on a bulb, buy the bulb, fit it or have it fitted for a few pounds, and take the car back to the same station by the end of the next working day so the retest costs nothing. If it fails on aim, ask whether the tester can adjust it, check the dash beam dial is not left high, and consider leaving the car at the station, because aim is the one lamps item the free next day retest does not cover. If you are buying, a lamps line in the history is noise. A repeated aim failure, or a note that the light source and lamp are not compatible, is worth a question.
Figures in this guide: DVSA MOT testing data for Great Britain, initial failures by defect category for classes 1 and 2, 3 and 4, and 7, 2025 to 2026 total and quarterly, published 10 September 2026, and MOT test results by class of vehicle for the same period. DVSA MOT inspection manual for cars and passenger vehicles, section 4, as published on GOV.UK and read on 18 September 2026. GOV.UK pages "Getting an MOT: MOT costs" and "Getting an MOT: retest after a repair". Bumper headlight bulb replacement cost guide, updated 19 September 2025.
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