Private Number Plate Maker | Replacement Plates from £12.45

When you’re ordering a new set of number plates – whether standard, 3D gel, or 4D acrylic – it’s not enough for them to look good. To drive legally on UK roads, they must comply with BS AU 145e, the current British Standard governing all vehicle registration plates.

Yet, confusion abounds. Are black plates legal? Can you add a Union Jack badge? Is your 4D plate actually road – legal? The answer to all these lies in one document: BS AU 145e.

In this definitive 2025 guide, we break down exactly what makes a number plate legal in the UK, based on official standards, DVLA rules, and real – world enforcement – so you never risk an MOT failure, fine, or invalid insurance.

What Is BS AU 145e and Why Does It Matter?

BS AU 145e is the current British Standard for retro – reflective number plates used on UK vehicles, introduced in September 2021 to replace BS AU 145d. It sets strict technical and visual rules to ensure plates are:

Clearly legible to drivers and ANPR (Automatic Number Plate Recognition) cameras
Durable in all UK weather conditions
Consistent in design nationwide

Unlike optional guidelines, BS AU 145e compliance is mandatory by law under the Road Vehicles (Display of Registration Marks) Regulations 2001 (as amended). Any plate sold in the UK must meet these standards to be considered road legal.

According to the UK Government’s official guidance, using non – compliant plates can result in a £1,000 fine and vehicle failure during MOT testing.

BS AU 145e Number Plate Requirements: The Legal Checklist

To be fully compliant, your plate must meet all of the following criteria:

1. Correct Colour and Background

Front plate: White background with black characters
Rear plate: Yellow background with black characters
Both must use retro – reflective material (not matte or glossy finishes)

Any deviation, such as tinted backgrounds, white rear plates, or coloured characters is illegal.

2. Charles Wright Font Only

All characters must use the mandatory Charles Wright 2001 font, with exact proportions, spacing, and stroke width. This font was specially designed for ANPR readability.

Custom fonts, stylised letters, or “slim” variants are not permitted, even if they look similar.

The DVLA’s vehicle registration rules explicitly prohibit modified fonts. If you’re after maximum visual impact without compromising legality, 5D number plates offer a striking dual-layer depth and high-gloss finish – all while using the correct Charles Wright font and meeting BS AU 145e standards.

3. Precise Character Dimensions

Character height: 79mm
Character width (except “1” and “I”): 50mm
Character stroke thickness: 14mm
Space between characters: 11mm
Space between groups (e.g., AB12 CDE): 33mm

Even a 1mm deviation can render a plate non – compliant.

4. Legal Spacing and Layout

No additional gaps, symbols, or borders between registration groups
The registration must be displayed in a single line (except on motorcycles)
No slogans, logos, or decorative elements within the character zone

5. Mandatory Manufacturer Markings

Every legal plate must display:

The name or trademark of the manufacturer
The BS AU 145e compliance mark
A unique identifier (e.g., postcode or supplier code)

These markings must be permanent, non-removable, and positioned at the bottom centre or bottom right.

As noted by the Institute of the Motor Industry (IMI), many aftermarket plates omit or hide these markings – making them instantly illegal. For full details on legal number plate requirements, the GOV.UK number plates guidance outlines all mandatory specifications for suppliers and vehicle owners.

Are 3D Gel and 4D Number Plates Legal Under BS AU 145e?

Yes, but only if they meet all BS AU 145e rules.

3D gel plates: Use raised resin characters in the correct Charles Wright font. Legal if spacing, colour, and reflectivity comply.
4D acrylic plates: Laser – cut acrylic letters mounted on reflective base. Must not alter character dimensions or add illegal borders.

The material itself isn’t the issue – it’s whether the final product matches BS AU 145e specifications exactly.

However, the UK MOT Inspection Manual (Section 6.1.2) states that plates with “non – standard characters, poor retro – reflection, or incorrect dimensions” will fail MOT, regardless of aesthetic appeal.

Tip: Always buy from a DVLA – registered number plate supplier – they’re legally required to verify your identity and entitlement and produce BS AU 145e – compliant plates.

Common BS AU 145e Mistakes That Make Plates Illegal

Even well – meaning buyers often end up with non – compliant plates. Here are the top violations:

Tinted or “stealth” plates: Reduce reflectivity → illegal
Custom spacing (e.g., AB 12 CDE): Breaks layout rules → illegal
Omitting manufacturer details: Required by law → illegal
Using non – reflective or carbon – fibre backgrounds: Fails reflectivity test → illegal
Adding logos, flags, or icons within the character zone: Not permitted → illegal

Note: National flags (Union Jack, Welsh Dragon, Scottish Saltire) are allowed, but only in the designated left – side badge area and only on plates made after September 2021 – and they must not interfere with legibility.

For full details, refer to the GOV.UK page on national identifier flags.

How to Check If Your Plate Is BS AU 145e Compliant

Before fitting a new plate, verify:

Reflectivity: Shine a torch at night—it should reflect brightly, not appear dull or glossy.
Font & spacing: Compare characters to a known legal plate. Use a ruler to check dimensions.
Manufacturer marking: Look for “BS AU 145e” and supplier details at the bottom.
Colour: Front = white, rear = yellow—no exceptions.

If ordering online, ensure your supplier uses a real – time compliance checker in their plate builder tool. At Private Number Plate Maker, our custom number plate maker enforces BS AU 145e rules automatically – so you can’t design an illegal plate.

What Happens If You Use a Non – Compliant Plate?

Driving with illegal plates isn’t just a minor oversight – it carries real consequences:

MOT failure: The tester checks plate legality as part of the inspection
Fixed penalty notice: Up to £1,000 fine
Insurance invalidation: If involved in an incident, your insurer may refuse to pay
Vehicle seizure: In extreme cases, police can immobilise your car

According to Police.UK guidance, officers are trained to spot non – standard plates during routine stops.

Final Thoughts: Legality First, Style Second

BS AU 145e exists to keep UK roads safe and ensure every vehicle is identifiable – by humans and machines alike. While it’s tempting to personalise your plate with unique fonts or colours, true customisation happens within the legal framework.

The good news? You can have stylish 3D, 4D, EV green flash, or ghost plates – as long as they follow BS AU 145e.

At Private Number Plate, we specialise in road legal private number plates that balance personal expression with full compliance. All our plates are BS AU 145e certified, made with premium materials, and produced by a DVLA – registered supplier – so you drive with confidence.

BS AU 145e Explained: What Makes a Number Plate Legal in the UK? (2025 Guide)