Window Tint Law UK: Legal VLT Limits Explained

UK law sets a legal minimum for how much light must pass through your car's windscreen and front windows, known as visible light transmission (VLT). Get it wrong and you risk a police light-meter check, a prohibition notice, and a fine, even if the tint job looks factory-standard.

The Legal Light Transmission Limits

The rules only set a minimum, not a maximum, for how much visible light must pass through certain windows. This is measured as a percentage of visible light transmission (VLT): the higher the percentage, the more light gets through, and the lighter the tint.

"Front side windows" means the windows level with the driver's seat, the ones you'd usually wind down or that carry a front door mirror, not the windows further back in the cabin.

Why There's No Limit on the Rear Windows

The legal minimums only apply to the front windscreen and the front side windows because these are the panes that matter most for the driver's own forward and side vision, and for other road users being able to see the driver. Rear windscreens and rear side windows are not subject to any minimum VLT figure, which is why you'll see plenty of cars with limousine-dark rear windows and privacy glass fitted entirely legally, while the front glass stays clear.

Factory Tint vs Aftermarket Film

Factory-tinted glass, fitted by the vehicle manufacturer, is built to comply with the relevant limits from new, so it is very rarely the cause of a problem. The usual issue is aftermarket tint film applied after the car is registered, most often to the front windscreen or front side windows, where an installer or owner has gone darker than the legal minimum allows, sometimes to match the factory-dark look of the rear windows without realising the front glass is held to a different standard. If you're buying a used car or a tint kit, check the manufacturer's specification or the film's stated VLT rating against the limits above before assuming it's road legal.

How Police Enforce the Rules

Officers can check a vehicle's window tint at the roadside using a handheld light meter, which measures the actual VLT percentage of the glass rather than relying on a visual estimate. If the front windscreen or front side windows read below the legal minimum, the vehicle can be issued with a prohibition notice, which stops it being driven on the road until the tint is removed or corrected, alongside a penalty notice or a fine. Because this is a vehicle condition and construction and use matter rather than a driving offence like speeding, the response is typically about getting the vehicle fixed rather than adding points to a licence, though the exact outcome depends on the circumstances and the officer's discretion.

MOT Tests and Tinted Windows

Window tint is also checked as part of the MOT test, under the visibility requirements for the windscreen and windows in the driver's line of sight. A tester who finds the front windscreen or front side windows tinted below the legal minimum can fail the vehicle on that basis, separately from any roadside stop. Getting non-compliant film removed before an MOT is due avoids a fail that would otherwise need sorting out anyway.

For other things that can get a car pulled over or checked at the roadside, see our guides to mobile phone driving law and penalty points. If you're weighing up a dash cam instead of tint for privacy or evidence reasons, see dash cam laws. For the wider picture, visit the UK driving laws hub and our guide to United Kingdom law.

This article is general information about UK vehicle window tint rules and is not legal advice. If your vehicle has failed a check or you're facing a prohibition notice or penalty, get advice from a solicitor, a garage, or Citizens Advice about your specific situation.