Beswad, if you do it on line you don't need any documents at all - DVLA check out while you are applying on-line that you have current MOT and insurance and you own the car. You need a number from the log book, and you pay £2.50 extra if paying by credit card - but it's dead easy, the site tells you what to do next. We have renewed our road tax on line for a couple of years now, no need to take docs down to the PO and queue, and they email a receipt to you so you have proof in case it gets delayed in the post. Do it now!