I hope you're joking mate

You'll need to go to your local DVLA office and change the Tax class back to "Petrol Car" from Disabled, they should let you tax it at the same time as well. You will NOT be able to do this at a post office so no excuse for a rant thread if you try there and get turned away

Just make sure you get the whole V5 from whoever you're buying it from, otherwise you'll be waiting 4 weeks+ to tax it.