Buying tax online ....can you do it for all cars?

I wanted to get my insurance online tomorrow and then get my tax on line but someone has told me you can only do it for some cars??? does anyone know anything about this?

Visit
http://www.direct.gov.uk/en/motoring/own...

It should tell you all you need to know

Think the online tax service should be fine for all cars.
Tax (road fund licence) is available for all vehicles on line, should be no problem at all
As long as you actually have insurance then you can get your tax online for any car. They check the database to make sure you have insurance and (if applicable - 3yrs+) MOT. Once you purchase your insurance and are covered you can buy tax online. Read the website: www.dvla.gov.uk
You need to have a "new-style" MOT certificate, if your car is old enough to have one of those. That is, one of the computerised ones, not the one that your nice little mechanic used to write out for you, and leave big oily thumb prints over!

Otherwise, check out the website. I've just renewed mine online; a word of warning, as the disc is sent through the post, and it can be lost. I know, as mine was, and I had to order a replacement (which arrived today - phew!), and I was unable to drive my car for this week (could get done for not showing a valid tax disc, even if it's paid for).
It shouldn't be a problem, I'm not aware of any restriction.
If you received notification that you can do so by the DVLA and provided you insurance is current and MOT is up-to-date, the answer is yes.