The easiest way is if you still have the V5 (log book) when you scrap your car is to go to https://www.gov.uk/sold-bought-vehicle/y/no/scrapped-it-or-it-s-been-written-off
Its really simple, all you need is the car registration, the 11 digit number off your v5 (log book) and the companys name and address you sold the vehicle to.
If you dont notify the dvla they could think its still on the road and you could end up with a road tax reminder, fine for not paying road tax and even worse bayliffs at your door.
Scrap cars Liverpool will do it for you so you have nothing to worry about and you will get an email from the dvla to notify you of it as seen in the above photo.
If you would like a price for your car you can get an online quote at Scrap my car
or call one of the friendly operators on 08007022137
For a more detiled explantion on scrapping you car go Scrap my car
Also you can see all the previous customers reviews at Scrap my car