Oh I got a receipt booklet for these things. It has spots for names, item names, serial numbers, price, signatures and comments. I'm also taking pictures as well!
I got screwed a while back by my ex best friend. I bought his bass guitar, he found out I was selling it and got pissed and his mom called the cops on me and photoshoped a myspace comment saying I'm selling it because I was pissed..... Yeah fucked up! So I beat his ass, and now I do this with every paperless transaction, trust no one when money is involved!