Road Tax (VED)

Just read that road tax is changing next April but still not quite sure that I understand what the new rules will be. My understanding is that all G Wagons (which I assume emit more than 332 g/Km of carbon) will be subject to the following annual charge:

From 1 year old to and including 6 years old a total of £450

From 7 years and older a total of £140

If I'm right then that's good news for what I am sure is the vast majority on here. If I am right then it must be worth thinking about cancelling my road tax from the last day of March 2017 and taking out fresh year's tax on April 1st as, for me it will mean a saving of £70 which is three quarters of a tank of petrol.

http://www.motoring.co.uk/dvla-licensing/2017-road-tax-rules-and-how-to-...

Or maybe I've got it all wrong so if you read this differently please let us know.

edit:- Sorry - just realised that this is only for vehicles registered AFTER April 1 2017.