UK number plate rules explained (BS AU 145e)

1. The standard: BS AU 145e

Every plate fitted since 1 September 2021 must meet British Standard BS AU 145e, which governs the plate's reflectivity and durability. You can't see the standard by looking at a plate — which is exactly why the law requires compliant plates to be marked: a legal plate carries “BS AU 145e” and the details of the supplier who made it. A plate with no markings wasn't made to the standard.

2. Colours and background

• Front plate: black characters on a white retroreflective background.
• Rear plate: black characters on a yellow retroreflective background.
• Characters must be a single shade of black — no two-tone, outlines, colours or “carbon-effect” finishes.
• The background must have no pattern.
• Raised characters are allowed — GOV.UK states plates can have 3D (raised) characters, which is what makes compliant 3D gel and 4D plates legal.

3. Font and character sizes

There is one prescribed character style (widely known as the Charles Wright font) and one set of dimensions for standard car plates, set out in DVLA leaflet INF104:

• Character height: 79mm
• Character width: 50mm (except the figure 1 and letter I)
• Stroke (the thickness of the black): 14mm
• Space between characters: 11mm · space between the two groups: 33mm

Motorcycles and some imports use a smaller two-line size (64mm-tall, 44mm-wide characters with a 10mm stroke and 10mm spacing). Square and two-line plates follow their own fixed layout in INF104. If a font is stylised, squashed, or “almost” right, the plate is illegal — there is no tolerance for creative typography.

4. Spacing and grouping

A registration must be displayed in its legal grouping — for a current-format registration that's “AB12 CDE”, never “A B1 2CDE” or squeezed together to spell something. Mis-spacing a plate is one of the most common ways drivers turn a legal registration into an illegal plate. The formats and the exact rules are in our spacing guide.

5. Flags, identifiers and the green flash

Plates can display certain flags, symbols and identifiers on the left-hand side, and fully zero-emission vehicles can display a green flash. The permitted set is defined on GOV.UK — anything outside that list (club badges, novelty symbols, sponsor logos) makes the plate non-compliant.

6. The penalties

Drive with incorrectly displayed plates and you can be fined up to £1,000 and the vehicle will fail its MOT. The rules are checked at every MOT, so a non-compliant plate isn't a “risk you might get away with” — it has a built-in annual checkpoint.

Who's allowed to make plates at all

Number plates can only be supplied by businesses on the DVLA's Register of Number Plate Suppliers — supplying plates unregistered is illegal. Registered suppliers must verify a buyer's entitlement and identity before making a plate and keep records the DVLA, police and Trading Standards can inspect. That's why every legitimate seller asks for documents — and why we do (RNPS No. 75456).

Quick answers

Need a plate that's actually legal?

Build yours in our configurator — legal font, sizes and spacing are applied automatically, and every order is entitlement-verified before you're charged. If a combination isn't road-legal, it won't let you build it.

Related guides

• Are 4D number plates legal? (2026 guide)
• Number plate spacing rules (and why they matter)
• Are 3D gel number plates legal?
• Show plates vs road-legal plates