I had that with a car I sold,when I got tax renewal form I just wrote to them telling them I had sold it,I told them I had sent my papers in but he couldnt have done.I told them I couldnt remember his name and address,I never heard anything else about it and that was about 8 years ago.Son in law who is a motor trader has this all the time,he gets penalty points notices,congestion charge notices etc.he writes back to the relevant authority and doesnt hear anything else about them.