42 CFR 423.36 - Disenrollment process.
(a) General rule. An individual may disenroll from a PDP during the periods specified in § 423.38 by enrolling in a different PDP plan, submitting a disenrollment request to the PDP in the form and manner prescribed by CMS, or filing the appropriate disenrollment request through other mechanisms as determined by CMS.
(b) Responsibilities of the PDP sponsor. The PDP sponsor must -
(2) Provide the enrollee with a notice of disenrollment as CMS determines and approves; and
(3) File and retain disenrollment requests for the period specified in CMS instructions.
(c) Retroactive disenrollment. CMS may grant retroactive disenrollment in the following cases:
(1) There never was a legally valid enrollment; or
(2) A valid request for disenrollment was properly made but not processed or acted upon.