There are four status codes for a motor vehicle, as defined by ENatis are:

Code 1 – New 
New vehicles delivered/sold by a dealer to the first owner. 

Code 2 – Second-Hand 
Used/pre owned vehicles with one or more previous owners/registrations. 

Code 3 – Permanently Unfit For Use 
Code 3 vehicles are Code 1 or Code 2 vehicles that have been involved in an accident and which, according to the insurer, is so badly damaged that it is not worth repairing. To the insurance company the cost of fixing the damage would amount to more than the car’s value at that particular time.
Code 3 vehicles are usually sold for a lot less than Codes 1 and 2  cars. Is it a good idea though to invest in a Code 3.

Code 4 – Permanently Demolished 
A vehicle falls into this category when the chassis of the motor has been: 
a.) Compacted; 
b) Compressed; 
c) Melted; 
d) Destroyed; or 
e) Damaged to such degree that it cannot be made roadworthy.

Why buy a Code 3 car?
When the insurer has written the vehicle off it does not necessarily mean that another person/institution cannot fix it or sell it again. 

If after the damage has been restored the previously ‘unfit’ car successfully completes a roadworthiness examination/test, it is legally allowed to be driven on our roads again.

So, Is it worth buying a Code 3 car – Yes or No?

https://www.traditionrolex.com/46

In summary the general opinion is.

Yes – The price will be very low.

No – The cost of repairs plus the cost of the damaged car might be more than just buying a similar aged, legal and on-the-road version of the vehicle. It could be that the buyer is a car enthusiast with mechanical interests or a close association with a group of similarly minded experts or a business that repairs badly damaged cars. However, do your sums very carefully.