Most MDs in Canada bill the Medical Services Plan (with various names in different Provinces) for services - set amounts for specific items, eg. routine office visits, writing prescriptions, C-section, etc. I'm not sure how complications are handled. Some things such as writing a sick note for work, driver's and pilot's license physicals, or removal of non-threatening moles are billed directly to the patient.

A few MDs such as pathologists, anaesthetists and radiologists, are paid a salary by the hospital or regional health authority.

There are a few for-profit clinics (an increasing number), including some that perform advanced surgery, but (in BC at least) they can't do procedures that are normally covered by the MSP. They mostly do things like elective plastic surgery and cases for the Workers Compensation Board, the police or the Armed Forces. These patients "jump the queue" and get quick treatment, usually much quicker than other patients.

I don't really know enough of the details to say how complex the whole thing is (though I'm sure it is satisfying to bureaucrats) - but it's dead simple for patients. Present your medical ID card (if you aren't already a patient entered in the the clinic or hospital system), and you are taken care of. No bills are ever received, except for things like private rooms in hospitals (and if those are the only rooms available, you don't get billed for that either.) Ambulance trips are billed to the patient relatively cheaply - $80 or so per trip.

The system has it flaws, for sure - wait times are much too long, and a lot of people have a hard time finding a family doctor, but these problems are being addressed (not quickly enough, but going in the right direction) - but overall it's good. No citizen ever doesn't get treatment no matter how much money they have or don't have. And your premiums don't go up every time you get sick.

(Non-citizens are a different matter - a stay in an ICU can set you back $2500 a day or more).