I sold my car 5 weeks ago and the new owner has received the new log book,but this morning i got the notice reminding me to tax it end of september or do a sorn on it, i have realised i used the old blue log book and not the new replacement red books that were issued a while back when selling it, but because new owner got the log book back i just thought it was alright, should i just ignore the notice or send in the red log book.