Registration Plate Lamp Inoperative: The Little Bulb That Fails MOTs

Nobody checks this bulb. Almost nobody knows it exists until the MOT certificate arrives with a line like:

Registration plate lamp inoperative in the case of multiple lamps (4.7.1 (b) (i))

Registration plate lamp inoperative in the case of a single lamp or all lamps (4.7.1 (b) (ii))

In short: a number plate light is out. If the car has two or more and at least one still works, it is a Minor defect and the car passes. If the only lamp, or every lamp, is out, it is a Major defect and the car fails.

What the Two Versions Mean

Most cars have two small lamps above the rear number plate. If one of several is out, that is 4.7.1 (b) (i): a Minor defect, recorded on the certificate but not a failure. If the car only has one plate lamp and it is dead, or every plate lamp is out, that is 4.7.1 (b) (ii): a Major defect, and the car fails. The rule exists for a plain reason: an unreadable plate at night defeats the entire point of having one.

Why Plate Lamps Die Unnoticed

• They live in the wettest, dirtiest spot on the car: the back panel, in the spray zone, often in a housing whose seal gave up years ago.
• Corroded contacts and earths are as common as failed bulbs: the classic symptom is a lamp that flickers with the boot lid.
• They are only on with the sidelights, at night, behind you: the one combination a driver never sees.
• On LED units the whole housing often has to be replaced, but the principle is the same: it must light.

While You’re Back There: the Plate Itself

The MOT also cares about the number plate the lamp is lighting. A plate that is deteriorated, delaminating, dirty enough to be misread or displaying the wrong spacing attracts its own defect under section 0.1, and the same faded plate can also earn you a roadside fine. If yours is past its best, sort both at once. Our guide to what the characters on a number plate mean covers the format rules.

The Ten-Second Check

Tonight, sidelights on, walk to the back of the car. If you can read your own plate, section 4.7 is yours. While you are there, press the brake pedal against a wall or window for the stop lamps, and run round the indicators. Lighting is the biggest failure category in the country, and almost all of it announces itself to anyone who looks.

Bulbs Fitted While You Wait

Any of our 12 branches across Nottinghamshire will replace a plate lamp bulb while you wait, and if the fault is a corroded holder or earth we will fix that properly rather than leaving you to meet the same defect next year. Book an MOT online, or set up a free MOT reminder so the date never surprises you.

Two plate lamps above a van’s rear plate: when the only lamp, or all of them, go dark, the defect is Major and the vehicle fails.

Every lamp above this plate was dead at our Stapleford branch. When they all go together, suspect the feed or a shared corroded earth rather than coincidence.

Frequently asked questions

Will my car fail its MOT for a number plate light?

If every plate lamp is out, or the only one fitted is out, yes: that is a Major defect under 4.7.1 (b) (ii). If just one of two or more lamps is dead it is a Minor defect: recorded, but the car passes.

Why does my number plate light keep blowing?

Usually it is not the bulb’s fault: water in a perished housing corrodes the contacts, kills earths and mists the lens. Replacing the bulb without curing the leak just books the same failure for later, which is why we check the holder as standard.

Can a dirty or faded number plate fail the MOT?

Yes: a plate that is deteriorated, delaminating or dirty enough to be misread is a defect under section 0.1, and incorrect spacing or fonts are treated the same way. A faded plate can also attract a roadside fine, so it is worth replacing on its own merits.

How much does it cost to fix a registration plate lamp fault?

It depends on the underlying cause and the vehicle, which is why we always inspect first. Once we can see exactly what is needed we will explain it in plain English and confirm the price with you before any work starts.