Payment not guaranteed.

Have you ever looked at a pre-authorization notice for, oh, let's say, a surgery. If you have you would have certainly noticed the following disclaimer, "pre-authorization does not guarantee payment."

What the hell is that. I simply am unable to comprehend it. What the insurers are saying, unless I'm missing something, is that despite getting permission to do the procedure, despite the carrier's determination that the procedure is warranted, despite the determination that the patient has coverage for the procedure, and despite the determination that you are a participating provider, you may, in fact, get stiffed on payment. Interesting.

To me, that is like going to a restaurant, ordering a burger, acknowledging the price for the burger, ordering, eating it, and then saying, "nahhh, I'm not gonna pay for it. The burger that you provided was not really a beef burger, in my opinion, and that is what I ordered. You can appeal my decision though." Of course, that would be crazy, not to mention illegal.

Yet that is what happens daily to physicians across the country, in all specialties. Will someone please explain to me, like I'm 5, what "payment is not guaranteed" means.