Few car modifications cause as much confusion as window tinting law. Some drivers think all tint is illegal; others fit blackout film to their front windows and are shocked when they're pulled over. The truth sits neatly in between, and once you understand one simple number — VLT — it all makes sense.
What is VLT (Visible Light Transmission)?
UK tint law is built around Visible Light Transmission (VLT): the percentage of visible light that passes through the glass. A higher percentage means lighter glass. A film described as "70%" lets 70% of light through and looks almost clear; a "5%" limo film lets through just 5% and looks near-black.
Importantly, the legal figure is the combined VLT of the glass and any film together — not the film on its own. Factory glass already blocks a small amount of light, so even a "light" film can push you over the limit on the front windows.
The legal tint limits in the UK
For vehicles first used on or after 1 April 1985:
- Front windscreen: must transmit at least 75% of light.
- Front side windows: must transmit at least 70% of light.
For vehicles first used before 1 April 1985, both the windscreen and the front side windows must transmit at least 70% of light.
And the part everyone loves: there are no legal limits on the rear side windows or the rear windscreen. You can tint the back of the car as dark as you want — including full limo black — and stay completely legal, provided the car has functioning door mirrors on both sides (which every modern car does).
Why installers won't tint your front windows dark
Because the 70% limit includes the factory glass, there's very little "headroom" to add film to the front side windows. Even a light film typically drops the combined VLT below 70%. A reputable installer will decline to fit dark film to your fronts — not to be awkward, but because it would make your car illegal. If someone promises dark, legal front tint, they're either mistaken or misleading you.
How police and DVSA check tint
Officers use a calibrated tint meter that clamps onto the glass and reads the exact VLT. It takes seconds. If your front glass reads below the legal threshold, the reading is your evidence — there's no arguing with the number.
Penalties for illegal tint
If your front tint is too dark, you can expect:
- A prohibition notice requiring you to remove the film before driving further, or immediately.
- A penalty notice or fine.
- The cost and hassle of having the film professionally removed.
Businesses that fit or sell over-tinted front glass can also face action. In short, illegal front tint is never worth it.
Tint and your MOT
The MOT assesses the driver's view of the road. Tint that's too dark on the windscreen or front side windows can result in a failure or an advisory. Tint on the rear windows is not assessed as part of the driver's forward view, so dark rear tint won't fail your MOT. If you're buying a used car with front tint, it's worth checking it's within limits before test time.
Staying legal and looking good
The sweet spot for most drivers is simple: go dark on the rear windows and rear screen for privacy and style, and either leave the fronts clear or add a barely-there film that stays above 70%. This gives that sleek, factory-plus look without any legal risk.
At Wizz's Wraps we tint hundreds of cars around Staffordshire and we'll always fit within the law. We'll measure, advise on the right combination for your car, and make sure you drive away looking sharp and staying legal.
Book Window Tinting in Stoke-on-Trent
At Wizz's Wraps in Tunstall, Stoke-on-Trent, we've tinted everything from daily runarounds to show-stopping supercars. Every install uses premium, professionally cut film, is fitted in our clean indoor bay, and is backed by our workmanship guarantee (1-year installation warranty plus 3–5 years on the film itself, depending on the product).
We only fit tint that keeps your car road-legal where the law requires it, and we'll happily talk you through the right shade for your vehicle. Pop in to 31a Parsonage Street, Tunstall, ST6 5HL, call us on 07533 621258, or request a quote through our website. We're rated 4.7★ across 182 Google reviews from drivers across Staffordshire.
