I think this is good. Any car that doesnt have a CO2 rating (usually because of its small production numbers) will have its taxable benefit assessed according to engine size. It just so happens that an Evo engine fits into the under 2 litre category so the tax benefit is 25% of the total new car value including furry dice and nodding dog. If it had a CO2 rating it would undoubtedly be the max i.e. 35%. This makes the Evo a good value company car to run. Lets not get the taxman too interested in this topic though!
Not wishing to pour cold water on this happy musing but...
I believe that if the car is not listed, and it it a grey import, then the max tax applies (35%). Although on what they base the list price, I know not. But you can bet your boots it won't be on the price you paid... but on more.
Currently, the new tax rules simply state that if a car does not have any emissions figures, for whatever reason, then the tax rate will be based on engine size alone. I've been constantly checking both online databases that are relevant to this, and will be very surprised if official figures for the Evo VI are ever generated. These databases can be found here: http://www.vca.gov.uk/frames/index.htm and here: http://www.smmt.co.uk/co2/co2.asp
As my car is an official Ralliart/Mitsubishi UK import, then I suspect that this is all I need to worry about. If your car is a grey import, then I am pretty sure that the tax man will still only be able to charge tax at 25%. As far as the price on which the tax is chargeable, this will be down to whatever value is put on the car by your accountants when they create your P11D. Usually, they will use the manufacturers list price for the car (assuming there is one), but if not, they will enter the actual purchase price when new (in the case of grey imports). The tax man can challenge this, but if you have documentary proof that this is what the vehicle cost when first registered, then I believe they will allow this price. At worst, the tax man may insist of using the list price of the nearest equivalent official car e.g. the GSR at £30,995.
If you've got any doubts about tax and grey imports, I suggest you talk to an accountant, and get him to look into it.
A lot of the financials depends on what you are offered as a cash alternative. In my experience a lot of companies where are are perks rather than necessary for the job have practically given up on giving cars and just give extra cash. For me this would probably be cheaper than having a company motor but an Evo is not an option anyway! I even make a few quid on the petrol allowance when I do mileage on company business.
There are a few other advantages to Evo company cars, such as if it's your own business then the cost of the car is tax depreciable for the company (to the extent that it is used for business). There was an case recently about a bloke who got a tax deduction for a Diablo which he ran as a company car. He supplied **** to night clubs in London and claimed (successfully) that the car was necessary to create a flash image with the nightclub owners etc, so was a legit. business purpose!