Quoted from Manimal:Always do a bill of sale on big items. Just good protection for both parties. I always list the price and include the terms such as being sold "as is" , or noted defect such as cabinet scrape, etc. I have them sign a copy and I keep one as well. If I don't know them, I ask for drivers license and list both our numbers. You just never know what circumstances will arise.
You would be the 1st one I ever encountered that did that