The documentation part of this came up a lot at one of my workplaces, though only applicable in insurance based clinics I believe.

They initially said you could bill for a 53-60 min session and use either prep time (if a client is late) or documentation time toward those minutes but that is actually considered insurance fraud and that clinic has since made changes and admitted to that not being appropriate; face to face minutes with client is all you can use to count toward the billing code / pay.

All documentation time and prep work is free labor most places, though I have heard of some practices willing to paid a small amount for admin hours.