I had group therapy one time where we weren't allowed to cancel at all even if we were sick or had an emergency. We were still expected to pay. However, it was only $25 a session.

With individual therapists, I've never really known their cancellation policies. I don't think I have ever been charged for canceling.

Most doctors require 24 hours notice for canceling although if they cancel nothing happens to them. My pdoc was sick the day of my last appointment and canceled the day of. I was able to see her later that week, but I know if I had been sick I would have had to pay.