What are the most common MOT failures?

The failure statistics are consistent year after year, and they are dominated by cheap items. A large share of failed tests could have been passed with an hour and a set of bulbs.

Step by step

1. Start with lighting and signalling.The largest single category. A dead bulb, a cracked lens, a misaimed headlight or a number plate light that nobody has looked at in years. Check every light on the car in one walk-round.
2. Check the driver's view of the road.Windscreen chips in the swept area, a cracked or missing mirror, a dashcam or air freshener obstructing the view, and worn wiper blades all sit in this category.
3. Look hard at tyres.Tread below 1.6mm anywhere it matters, mismatched sizes across an axle, cuts, bulges and exposed cord. All visible from a crouch and all straightforward failures.
4. Expect suspension to be the expensive one.Springs, dampers, bushes and arms corrode and wear, particularly on salted roads. You cannot inspect these safely yourself, but a knocking noise over bumps is the usual early warning.
5. Expect brakes to be the second expensive one.Pad and disc wear, corroded pipes, imbalance across an axle and handbrake efficiency. Never owner work. Grinding, a soft pedal or pulling under braking all mean a garage now, not at MOT time.
6. Do not overlook the small legal items.Registration plate spacing and font, a horn that does not sound, seatbelts that do not lock, a boot or bonnet that will not latch, and an exhaust that is blowing.
7. Deal with warning lights ahead of the test.Airbag, ABS, engine management, brake fluid and tyre pressure monitoring warnings are all failures. Getting the codes read beforehand is much cheaper than a wasted test.
8. Watch for corrosion in the wrong places.Structural corrosion within a defined distance of mounting points is a failure and is common on older cars. It is a good reason to be realistic about an ageing car's future.
9. Use last year's advisories as this year's list.The advisories on the previous certificate are a tester's prediction of what will fail next. It is the single most useful piece of paper you have.

Tips

• Keep the previous MOT certificate. The advisories on it are a free maintenance plan.
• The MOT history for any UK vehicle is publicly available online by registration — useful before buying, and useful for spotting a recurring advisory.
• An MOT is a snapshot of one day, not a guarantee for the year. It does not replace servicing.

Common mistakes

• Treating the MOT as a service — The test checks safety and emissions items to a defined standard on that day. It does not check the oil, the timing belt, the clutch or anything else that decides whether the car keeps running.
• Ignoring advisories for a year — An advisory means an item has started to wear. Left alone it becomes a failure, and often a more expensive one once related parts have been affected.

If it doesn't work

Questions people ask