I've never paid road tax.
I do pay VED though, and that's going up too... by the same amount as it happens.
I believe it will go up from April 1st? So you should be ok on the old rate but don't take my word for it
It doesn't matter when you buy, the price you pay will be determined by when it's valid from. If your new tax disc is valid from today, you'll pay the lower price... but lose 21 days worth, as no one's going to do this the price has effectively gone up already as your new disc will be valid from 1st April you'll be charged April's prices. I'm not sure even I understand my explanation but on the bright side I know what I mean