UK Number Plate Legal Requirements
Number plates in the UK aren't just an identifier — they're a legal requirement, and the rules around how they must look are surprisingly detailed. Getting it wrong can result in a fine of up to £1,000 and an MOT failure. Here's everything you need to know to stay road-legal.
The Standard: BS AU 145e
All number plates sold and displayed in the UK must comply with the British Standard BS AU 145e (updated in 2021). This standard covers the materials, reflectivity, and construction of plates. Only plates supplied by a registered number plate supplier (RNPS) using compliant materials should be used on UK roads.
Colours
The rules on plate colour are clear and non-negotiable:
- Front plate: White background with black characters
- Rear plate: Yellow background with black characters
- Both plates must be reflective
- Tinted, smoked, or coloured acrylic covers are illegal
Character Font
All characters must be displayed in the Charles Wright font — the standard mandatory typeface for UK number plates. Decorative, italic, or stylised fonts are illegal, even if they look similar to the official font. The characters must be black and must not be 3D or contain patterns within the letters.
Character Size and Spacing
Precise dimensions are specified by law:
| Measurement | Required Size |
|---|---|
| Character height | 79mm |
| Character width (most) | 50mm |
| Stroke width | 14mm |
| Space between characters | 11mm |
| Space between groups | 33mm |
| Top, bottom, side margins | 11mm |
These dimensions apply to standard-format plates. Motorcycles use a different (narrower) format.
Plate Size
Standard car plates must be:
- Oblong plates: 520mm × 111mm (most common)
- Square plates: 279mm × 203mm (permitted on some older vehicles)
What You Can and Cannot Display
Permitted:- A GB identifier with the Union flag, Cross of St George, Cross of St Andrew, or Red Dragon of Wales
- The name and postcode of the supplying dealer (in small print at the bottom)
- A 3D effect on characters (as long as they remain clearly legible and meet font standards — check with your supplier)
- Any flag other than those listed above
- Coloured or patterned backgrounds
- Rivets through characters
- Anything that obscures or alters the registration number's legibility
Fixing Your Plates
Plates must be securely fixed and clearly visible. A plate that is dirty, cracked, poorly lit at night, or hanging off the vehicle can lead to a police stop, a fine, or an MOT failure. Rear plates must also be illuminated at night.
Consequences of Non-Compliance
- A fine of up to £1,000
- MOT failure — the vehicle will not pass its test
- Police can require you to remove or replace a non-compliant plate on the spot
- Potential issues with ANPR (Automatic Number Plate Recognition) cameras, affecting insurance and road charging
It's always worth double-checking that any plate you buy — especially a private plate on a novelty-style board — meets the full BS AU 145e standard before driving on public roads.