As it happens I “Taxed” my 1980 Suzuki GS1000S yesterday and noticed the MOT exemption rules had been beefed up somewhat with additional guidance regarding substantial changes.

Your vehicle must have an MOT if it:

has been substantially changed
is a type or model of vehicle still in production
is a large vehicle being used commercially
has a registration number with a ‘Q’ prefix
is a kit car constructed from components from different makes or models
is a reconstructed classic vehicle (as defined by DVLA)
is a kit conversion where a kit body, chassis or monocoque is added to an existing vehicle, or vice versa

In general, a vehicle alteration is a ‘substantial change’ if the technical characteristics of the main components have changed.

The main components are the:

chassis
monocoque bodyshell
axles and running gear
engine
There are exceptions to that do not count as substantial changes to the main components.

My understanding was that kit cars have always been required to have an MOT?

I also have a Triton (Norton frame / Triumph engine for the uninitiated) that was first registered in 1966 – that might be an interesting conversation whether it has substantially changed as it still carries the same chassis and engine numbers as it did in 1966????

Slightly sideways but looking for a second hand Land Rover on the auction site – of two that claimed to be Historic so MOT exempt, neither had actually been registered as such and one had a Daihatsu engine and another a Discovery 5 cylinder diesel.

Perhaps part of the reason for the sales and caveat emptor I think!