I use one, even though they are no legally binding, but they do serve to prove that a kitten has been sold on the non active register and what that means. I did hear of someone who verbally explained about a non active kitten to a buyer who agreed at the time, but then changed her mind and demanded that the kitten be changed onto the active register. It ended up in small claims court and the court found in the kitten buyers favour as she claimed that she had not be told about the non active/active register and the breeder was forced change the kitten over. If you have something the person has signed then at least there's that worry crossed off. Doesn't stop them breeding from the cat and not registering the kittens though.