in the medical/health insurance business...?

what exactly is capitation vs. decapitation.

is decapitation just taking off the limits?

I worked in the medical insurance billing for years and never heard the term "decapitation" used. Are you sure this term was for billing instead of a diagnoses?

Capitation, as an example, is the HMO paying the primary doctor a set fee to be responsible for the care of that member, regardless of what is needed, to some extent of course. It might be like a retainer with a lawyer. A specified fee regardless if service is rendered.

Decapitation is what terrorists do. Beheading. Unless it is part of the above.