One of the main advantages of the MOT test is that the testing is standardised. Whether you take your car to a garage in Inverness or Plymouth, the testers work to the same checklist and are trained in the same way. Around a third of all vehicles presented for MOT tests fail. This is obviously bad news for the owners, who are faced with paying out for even more garage work to bring the car up to standard. The most frustrating scenario from a driver’s point of view is your car failing on a simple mistake which could have been easily rectified before presenting your car for inspection. If your car is due for a MOT soon, how many of these mistakes are you in danger of making?

Dodgy Number plates

We all like our cars to reflect our personalities. But if you’ve got a number plate which doesn’t conform to the rules, it’s an automatic fail. Number plates have to be white on the front, yellow on the back. The letters have to be the right size, and in the correct font. You’re also not allowed to mess around with the spacing of the letters and the numbers to spell words, or use the bolts to turn one letter or digit into another. A new number plate can cost as little as £20. 

Too Many Stickers

One of the key checks in a MOT is visibility from the windscreen. Anything which affects your vision is going to be another reason for a fail. Most drivers take this to mean cracks, or tinted films applied to windows to make them darker. However, too many stickers on the windscreen can be classed as blocking vision too. Remove all the stickers before the test so you’re not paying mechanic wages to do the job for you. 

Worn Tyres

Worn Tyres

If your car fails the MOT for having tyres which don’t meet the legal minimum for tyre tread depth, then that’s classed as a dangerous fault and you won’t be able to drive the car until it’s fixed. Everyone knows the best prices are available when you shop around, and not being able to take the car away limits that choice somewhat. Get into the habit of checking tread depth regularly so you’re not caught out. 

Windscreen Washers

Another common reason for failure is a problem with the windscreen washers. Either the jets are blocked and they’re not working at all, or even worse, you’ve forgotten to top up the washer fluid. The mechanic doing your MOT will check both, so make sure you’ve done the routine checks before taking the car in.

Sound the Horn

The MOT tester will sound the horn on your car and make sure it can be heard loud and clear. This is something you can easily test yourself. If it sounds weak, or cuts out, get it looked at first. If you’ve modified your horn to have a two tone sound, or some sort of non-standard gong, bell or siren, change it back as it won’t pass.



There are strict rules about your lights being in a good state to pass the MOT test. This is another very simple test which you don’t need mechanical knowledge for. Just switch the lights on and see if you spot any broken bulbs, dim spots, flickers or other problems. Changing bulbs is a fairly straightforward job, and there are videos online showing you exactly what to do.

Windscreen Wipers

Changing wipe blades isn’t a big job, so if you’ve noticed smearing or just that they’re not as efficient as they used to be, order a new set online or go to one of the major motoring stores. Look in the manual if you’re not sure which size of blades to get. Usually, it’s just a case of sliding one set of blades out, and replacing them with new ones. A new set of wiper blades can cost less than a tenner. 

Seats and Seatbelts

The MOT tester will want to make sure the driver’s seat can be fully adjusted, if it’s been designed to be adjustable. That means making sure it slides back and forth and can also be raised and lowered. Similarly, the MOT tester will tug on each of the seatbelts to make sure they would lock inn the event of a crash. If you’ve noticed problems with the seatbelts then deal with it straight away. It’s as much a matter of your safety as it is about passing the MOT. 


If your driver’s side mirror is hanging off or missing, it’s perhaps surprising to find out this isn’t an automatic MOT fail. The checklist requires a passenger side mirror which can be adjusted, and a rear view mirror. Again, there shouldn’t be stickers or anything else on the mirror to obscure the view. If the mirror is sticky, try loosening the mechanism with some oil or grease. If this doesn’t work, get the professionals to take a look. 

Fuel System

Not all problems with the fuel system can be spotted by the layman. However, if your fuel cap regularly sticks while you’re trying to fill the car, if it doesn’t fit properly or is missing entirely, that’s another reason for a fail. If you spot drops of petrol on diesel on the ground where you’ve parked your car, that’s indication that you may have a fuel leak which should be investigated right away.

Of course, you could do all of these checks and still fail the MOT for faults you were unaware of. When you drop your car off for its MOT, ask the mechanic to give you a ring if there’s a problem. You can then discuss options for repair, and get professional advice about how much it’s going to cost to get the repair certificate. If minor faults are indicated on the pass certificate, try to have these fixed before the next test date rolls around.

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