MOT INSPECTION / VOSA RULES
Windscreen MOT rules UK, what size chip or crack fails?
A chip larger than 10mm in Zone A (directly in front of the driver) fails. A chip larger than 40mm in Zone B (the rest of the wiper-swept area) fails. Damage outside the swept area is not tested. Repair is almost always cheaper than failing and rebooking.
ZONE MAP
Zone A and Zone B explained.
The MOT inspector checks for vision-impairing damage in two zones, both within the area swept by the wipers.
Inspector logic
- A1Identify the area swept by the wipers when in operation.
- A2Mark the 290mm strip centred on the steering wheel: that is Zone A.
- A3Anything in Zone A larger than 10mm is a fail.
- B1The rest of the swept area is Zone B. 40mm limit.
- C1Damage outside the swept area is not tested.
SIZE LIMITS
Pass / fail thresholds.
| Zone | Maximum damage size | Result | Visual reference |
|---|---|---|---|
| Zone A | 10mm | Any damage over 10mm fails | Smaller than a 5p coin (18mm) |
| Zone B | 40mm | Any damage over 40mm fails | Smaller than a £2 coin (28mm) |
| Outside swept area | n/a | Not tested, will not fail MOT | Anywhere outside wiper sweep |
Repair before your test date
A properly repaired chip passes an MOT in almost every case. Get it done before the test (£40 to £70, often free on insurance) rather than after a fail (full retest fee plus the repair anyway). Most chains offer a same-day mobile slot.
Driving with a cracked windscreen
Police can issue a fixed penalty notice if windscreen damage impairs vision, even before your MOT is due. The relevant offence falls under the Road Vehicles (Construction and Use) Regulations. If the chip is in Zone A and over 10mm, treat it as urgent.
FAQ
Can a repaired chip pass an MOT?+
Yes, in almost all cases. A properly cured resin repair leaves a small visible mark that does not impair vision. MOT testers assess windscreens against vision-impairing damage thresholds, so a clean repair below the size limit passes. The exception is a Zone A repair where the residual mark is still over 10mm wide, which would fail.
Is a crack at the edge of the windscreen an MOT fail?+
If the crack runs to the edge of the glass and is in Zone A or B (the wiper-swept area), it is an MOT fail and a structural concern. Edge cracks compromise the bond and tend to spread. Replacement is usually the only fix because resin injection cannot stabilise an edge crack.
Can I get a free retest if I fix the windscreen?+
Yes, in most cases. If your car fails on a windscreen defect and you leave it at the test centre, you get a free partial retest within 10 working days. If you take the car away first, the centre may charge for a full retest. Have the chip repaired or screen replaced before going back.