this was my first thought.I sold a Harley a few years back and the guy didn't turn in the title. I started getting bills for taxes on it. I contacted him and found out he had just put an old plate on it. Said he was too busy to get it done but immediately did so when he heard I was getting bills. It was a nightmare to get it squared away with the tax office. So by not turning in your title you are also putting the previous owner in a mess. Food for thought.