Previous British Standard BSAU145d

This Knowledge Base article provides you with some basic information on the British Standard BSAU145d. Which regulated every new number plate made between 2001 and 2021.

The British Standard

BSAU145d was the standard all number plates where manufactured to before BSAU145e. The new standard 145e became legal at the start of 2021, before becoming mandatory from 1st September.
British Standard certified components or number plates, just part of your obligations as a supplier BSAU145d
British Standard 145d is a statutory instrument or law, which was passed by the British Parliament in 2001. And it was designed to build upon and amend the previous specification 145a. To clarify, it sets out number plate characteristics with respect to visibility, reflectivity and strength. Alongside the regulations that govern plate illumination and placement on a vehicle.

BSAU145d Tests

Number plates are mostly printed out and are made up from assembled plate components. Before a component can be sold, number plates made from them need to be tested to BSAU145d standards. Only then can number plates made from those components carry a BS Number.

Tennants number plate production and testing
In order to pass 145d specifications a number plate construction has to pass 9 tests. Each test has a separate and distinct purpose, from ensuring legibility to checking durability.

Details of the tests can be seen below:


A number plate must be retroreflective, which means it reflects light back the same way it arrived. This is an important safety feature that also increases the plate visibility. The standard states the digits and background must have different levels of retroreflection. And different angles are checked in the dry and wet.


Chart showing luminance values
Number plates have rules governing their overall colours. Backgrounds have to be white or yellow and the digits black. As a result two elements are tested, the chromaticity and luminance. Chromaticity measures the hue and saturation. And luminance measures the level of light emitted.


British number plates are resistant to bending, because they need to stay fixed to a vehicle. Notably, on a curved surface like the rear of a vehicle. The standard states that if a number plate bends more than 25mm it fails this test.


From car polish to washing chemicals, tar to grit salt, all sorts of chemicals can end up in contact with a plate. Number plates are tested to ensure they can retain their integrity after exposure to solvents.


From being outside on a vehicle, a number plate is exposed to the weather constantly. Yet regardless of the conditions, it needs to remain legible without fading. To check a plates resistance to the weather it is exposed to over 2000 hours of UV testing.


Salt water testing unit for corrosion tests
Like solvents number plates are tested to check their resistance to corrosion. In the long run corrosives cause delamination, or make the registration number unreadable. To test its resistance, a saline solution is sprayed onto the plate over 230 hours.


Driving on our roads exposes a number plate to endless stones, chips and minor bumps. An impact test checks a plate’s durability to these constant small impacts. A projectile of 1kg is dropped onto the plate multiple times. Failure occurs if the plate delaminates, or cracks appear outside the impact site.


The UK’s changeable weather creates a testing environment for number plates. For example, changing from dry to wet and hot to cold puts stress on the construction. Thermal tests are run to simulate our climate, exposing a plate to 5 days of shifting temperatures. Any fading, blistering, cracking or delamination results in a failure.
Number plate holder for Thermal testing


Weathering tests include a test checking the effect of dirt and grime. Number plates are legally required to be readable, so the construction is tested for its resistance. Dirt consisting of a specific solution is applied to the plate and left for 3 days. Then it’s washed off and luminance and retroreflective tests run. Any loss over allowed limits results in a failure.

Number Plate Components

Registered suppliers have to produce number plates that meet the current standards. Unless they’re a manufacturer, they will purchase plate components from a third party, such as Tennants UK. These components will need be from a construction that’s passed British Standard tests. That way as their customer, you’ll be able to use their BS Certification.

Our Hybrid number plates

We test regularly and are certified for each construction of number plate we offer. To our customers we offer these constructions as matched components. But our certification only covers specific matched combinations. And we only authorise its use for those specific components.