A chip you barely notice on the morning commute can become a problem at test time. The NCT (National Car Test) checks roadworthiness, and windscreen damage can mean failure if it compromises visibility or the condition of the glass. It assesses the car as presented, so damage that spreads before the appointment may also turn a straightforward repair into a replacement bill.
Position matters, not just size
A chip directly in the driver’s line of sight deserves particular attention, especially within the area cleared by the wipers. Its appearance on a parked car does not tell the whole story: fractured glass can scatter light from approaching headlights or low autumn sun, making a seemingly minor blemish more distracting when the road ahead is wet and visibility is already reduced.
That does not mean every small chip automatically fails, or that damage away from the driver’s view is automatically acceptable. The location, type and extent all matter; check the current NCT windscreen criteria and ask a glass specialist to assess repairability rather than relying on a coin-size comparison or assuming that an old chip is harmless because it has stayed unchanged.
How autumn can worsen damage
The next question is whether the damage will stay repairable. A chip creates a weak point, and uneven heating, body movement over rough surfaces or another impact can encourage a crack to spread; during colder autumn mornings, avoid pouring hot water onto the glass and allow the demister to clear it progressively before driving, rather than trying to force a rapid thaw.
Waiting also allows moisture and dirt into the damaged area, which can affect the quality and appearance of a repair. A specialist repair uses clear resin to fill and stabilise suitable damage, but it may leave a visible mark; deep damage, spreading cracks, contamination or an unsuitable position can make replacement the more appropriate option, even when the original impact looked insignificant.
Where the replacement bill grows
Replacement costs more than filling a repairable chip because the glass must be removed, replaced and bonded correctly. On cars with a windscreen-mounted camera, the manufacturer may also require calibration—checking and adjusting camera alignment so driver-assistance features work correctly; ask whether the quote includes the correct glass, fitting and any required calibration, and check insurance terms for differences between repair and replacement cover, including any excess you would pay.
Arrange an assessment while the damage is still small, rather than waiting for the NCT to decide its fate. Tell the repairer where it sits and whether it has changed, and remember that a completed repair does not itself guarantee a test pass.