Do you have any insights regarding "time of
service discounts" to patients who pay at the time
the service is performed?
If you are asking for a legal opinion, I can't help you.
A time of service discount is a way to lower your fee to patients who pay cash at the time of service, saving you the administration costs of billing them or their insurance company. It has been a strategy to keep one's published fees as high as possible for third party reimbursement, yet with the ability to lower the fee for patients who lack insurance.
Apparently, this is a legitimate procedure if the amount of the discount could be justified to a jury of your peers as an accurate reflection of the true administrative costs you save by not having to bill and collect from a third party. I have heard that a 15% to 20% discount falls within what seems reasonable.
The time of service discount is not a cash discount because it is a policy that you offer to anyone, even third parties. But, as a practical matter, most insurance companies are not prepared to avail themselves of your generosity.