To Doctors, Clinics, and Hospitals:
DO NOT wait 2, 3, 6 months to send me a bill and then whine about how my account is overdue. No, actually, this isn't a 'reminder'. You can't remind someone of something you haven't told them yet! You certainly can't expect to charge interest on a debt you haven't told anyone about.
I do not care how long you decided to wait to get to my account or fart around with the insurance company. That makes YOU late not ME. Sticking passive-aggressive stickers on the bill is neither cute nor professional.