sometimes, but extra hours dont get paid extra, so very little incentive to do so. there are many different models for compensation but you can think of it as a 'fixed salary with optional bonuses'.

EDIT to add:

Most places have a base + bonus structure. You get your base salary, and you see patients, for each patient seen you generate 'RVUs' which is how your group/practice generates income ( by billing insurance companies ). Once you generate enough RVUs to cover your base salary, you start accumulating 'bonus' and that gets paid out down the line using whatever formula your employer uses. There is some variation to this but for the most part groups follow a similar scheme.

EDIT #2: This is US centric, i dont know how other countries do it.

Yes I don’t get the comments about salary vs hs. You need the same amount of people. The question is if you have 3 people doing 24hs shifts or 3 people doing 3 8hs shift a day… has nothing to do with more people/salary/money is just organization of work.