Will a Cracked Windscreen Fail an MOT?
A cracked windscreen will fail an MOT only if the damage is in the wrong place. A tester fails your car if damage over 10mm sits in Zone A, the strip in the driver’s direct view, or if damage over 40mm sits anywhere else the wipers clear. A chip smaller than that passes. So does damage outside the wiped area, unless it blocks your view of the road.
That is the whole rule. The rest of this page is what it means in practice: where Zone A actually is, what a fail costs you once you add the retest, and when a chip is worth repairing before test day instead of gambling on it.
The size limits, by zone
The tester divides the glass into the area the wipers clear (the swept area) and everything outside it. Inside the swept area, the limit depends on whether the damage is in front of the driver.
| Where the damage is | Fails if larger than | Plain-English location |
|---|---|---|
| Zone A | 10mm | The 290mm band straight in front of the driver, centred on the steering wheel |
| Rest of the swept area (Zone B) | 40mm | The wiped glass either side of Zone A, including the passenger side |
| Outside the swept area | No fixed size | Top edge, corners, blacked-out border. Fails only if it blocks the view |
These thresholds are in the DVSA MOT inspection manual and they apply to chips and cracks the same way. A 12mm crack in Zone A fails. A 12mm chip in Zone A fails. Location and size decide it, not what caused it.
Where is Zone A, exactly?
Zone A is a 290mm-wide strip centred on your steering wheel, inside the area the wipers clear. Sit in the driver’s seat and look straight ahead. The band of glass about the width of the wheel, level with your eyeline, is Zone A. It gets the strict 10mm limit because it is the glass you actually look through to drive.
Ten millimetres is small. Roughly a fingernail. Most drivers picture a windscreen crack as something dramatic and are surprised that a chip they can barely see is over the limit once it lands in that central band.
Is a small stone chip an automatic fail?
No. A 6mm chip in Zone A passes. Move that same chip to the passenger side and it can be up to 40mm before it fails. Roughly a quarter of cars fail their first MOT on something, but a single small chip on its own rarely is the reason.
The catch is spread. A chip that is fine in November sits through one hard frost, the glass flexes, and a crack runs out of it and into Zone A. Now it fails, and a repair that would have held is no longer an option. On the roads round Birmingham the potholes do the same job as the frost. A sharp jolt turns a stable chip into a running crack in one drive.
What a fail actually costs you
This is the part most guides skip. The MOT itself is capped by the DVSA at £54.85 for a car, and most garages charge £30 to £45. Fail on the windscreen and you are into the retest, and windscreen damage is not one of the items you can fix on the spot for a free same-day recheck. Those free items are things like a blown bulb.
So a windscreen fail usually means one of these:
- Get the glass replaced and return to the same test centre within 10 working days, and you pay a partial retest fee (a few pounds up to around £27, and some centres waive it).
- Miss the 10-working-day window, or go to a different centre, and you pay the full MOT fee again.
- Drive on the failed certificate in the meantime and you risk more than the retest, which the next section covers.
Retest fees vary by centre and the DVSA figures change, so check the live number on GOV.UK before you book. The point stands either way: a chip repaired before the test costs less than a screen replaced under time pressure plus a retest. Sorting it early is the cheaper path almost every time.
Is it illegal to drive with a cracked windscreen?
It can be, and a valid MOT does not protect you. Using a vehicle in a dangerous condition is an offence under Section 40A of the Road Traffic Act 1988. A crack that distorts your view, badly placed for low winter sun or night glare, can meet that test on any day of the year. A typical penalty is three points and a £100 fixed penalty, code CU20, and a court can go higher.
An MOT pass is a snapshot of one morning. It says the glass was within limits on the test date. It does not licence a crack that spreads across your eyeline in March.
Repair or replace before the test?
A resin repair works when the damage is small, in the right place, and hasn’t gone through both layers of the laminated glass. Once a chip in Zone A is over 10mm, or a crack is long, deep, or already spreading, replacement is the honest answer. Damage within about 5 to 7cm of the edge usually needs replacement too, because the edge carries the structural load and repairs there are unreliable.
One thing worth knowing before you replace: a properly done, near-invisible repair does not count as damage in the MOT at all. The tester judges a repair only on whether it distorts your view. So a good repair is not a patch that scrapes a pass. It is a genuine fix. If you’re not sure which way your damage goes, our windscreen replacement service in Birmingham will tell you straight whether a repair holds or the screen needs swapping, rather than selling you the bigger job by default.
The calibration part nobody mentions until the bill
If your car was built in roughly the last decade, there is a camera behind the windscreen running lane assist and automatic braking. Replace the glass and that camera usually needs recalibrating so it reads the road from the new screen correctly. Skip it and the safety systems can misjudge distances.
This is the hidden cost that makes a small repair look even better next to a full replacement. Repair a chip while it’s still repairable and there is no glass to swap and no camera to recalibrate. Leave it until it fails the MOT and you may be paying for the screen and the calibration together. It is the single strongest argument for not letting a chip sit.
Check your own screen in two minutes
Before you book, do the test yourself:
- Sit in the driver’s seat and find the band of glass the width of the wheel in front of you. Anything near 10mm there is a problem.
- Check the wider wiped area for anything near 40mm.
- Run your eye along the edges for cracks creeping inward toward the wiped zone.
- Look at the surround and seal for lifting or gaps.
Anything borderline, get it looked at before the test rather than after. A fail plus a retest costs more than a look and a repair, and it costs you the time of a second trip.
Common questions
Will a cracked windscreen fail an MOT if the chip is under 10mm?
No. Under 10mm passes in Zone A, and the limit is 40mm across the rest of the wiped area. It only becomes a fail if it grows past the limit or spreads into the driver’s central view.
How big is Zone A on a windscreen?
It’s a 290mm-wide band centred on the steering wheel, inside the area the wipers clear. Damage over 10mm here fails the test, which is stricter than the 40mm allowed elsewhere.
Can I drive to my MOT with a cracked windscreen?
If the crack makes the car dangerous to drive, you risk a Section 40A offence whatever your MOT says. If it clearly blocks your view, deal with it before you drive, not after the test.
Does damage outside the wiper area fail an MOT?
Usually not on its own. Outside the swept area it fails only if it genuinely blocks your view. A tester may still log it as an advisory if it looks likely to spread into the wiped zone.
How much does a windscreen MOT fail cost to put right?
The retest is the small part: a partial retest fee up to around £27, or the full MOT fee again if you miss the 10-working-day window. The real cost is the replacement glass and, on newer cars, the camera recalibration. A repair caught early avoids both.
Is windscreen damage covered by insurance?
Many comprehensive policies include glass cover, usually with an excess, and the terms differ a lot between insurers. Check your own policy wording before you decide whether claiming or paying direct works out cheaper.
Will a new windscreen need calibration?
If there’s a camera or sensors behind the glass for lane assist or automatic braking, yes, almost always. The camera has to be recalibrated to the new screen so those systems read the road accurately.
The full standard testers work to is published by the government: the DVSA MOT inspection manual, Section 3, Visibility.
Get it sorted before test day
If there’s damage that could fail, it’s cheaper to deal with it before the test than to pay for a fail, a retest, and a rushed replacement. We fit windscreens across Birmingham and the West Midlands and will tell you honestly whether yours needs a repair or a full replacement. Call 07897 528723 or get a quote.