I once had an institution tell me I needed to give them proof that my contracting "company" had insurance. I told them that wasn't going to happen, and they found a way to get around it. I was actually hoping they would just decide to not go through with the certification, because I had a suspicion, correctly as it turned out, that it was not going to be a pleasant experience. Just about the only time for me that working with a client was not a pleasant experience.