Available at specific times throughout the year for qualifying individuals such as those who are aging into Medicare (3 months before you turn age 65 to 3 months after the month you turn age 65) or are newly eligible for Medicare Part B.
questions.medicare.gov 
From January 1 until March 31, Medicare Advantage eligible individuals may make one enrollment request.
However, you are limited in the type of plan you can join. You can’t join or leave Medicare prescription drug coverage at this time. For example, if you have a Medicare Advantage plan with prescription drug coverage, you can only choose to join another Medicare Advantage plan that offers Medicare prescription drug coverage, or choose to return to the Original Medicare Plan and join a Medicare Prescription Drug Plan. If you don’t have Medicare prescription drug coverage, you can’t use this chance to get it.
The Open Enrollment Period (OEP) provides Medicare beneficiaries with one opportunity to enroll in, disenroll from, or change a Medicare Advantage plan. Like the General Enrollment Period, the Open Enrollment Period extends from January 1 through March 31 each year. Unlike enrollment in Part B, the change in Medicare Advantage enrollment or disenrollment becomes effective the month after the change is made.
Medicare Acronyms
General Enrollment Period (GEP)
Medicare beneficiaries who did not enroll in Part B when they first became eligible for Medicare may elect Part B coverage during the General Enrollment Period, which extends from January 1 through March 31 each year. Enrollment becomes effective on July 1 of the same year.
Medicare Acronyms
questions.medicare.gov
Special Enrollment Periods (SEP)
allow beneficiaries to make an enrollment change outside of the GEP, the AEP, the OEP and the L-OEP.
Medicare Acronyms
questions.medicare.gov/
The following individuals qualify to enroll anytime throughout the year:
| | Moved from another state within 60 days |
| | Dropped by an employer plan within 63 days |
| | Turned 65 in the past 3 months (or will turn 65 in the next 3 months) |
| | Newly eligible for Medicare Part B |
| | Qualify for some assistance through Medicaid |
A set time when you can sign up for Medicare Part B if you didn’t take Medicare Part B during the Initial Enrollment Period, because your or your spouse were working and had group health plan coverage through the employer or union. You can sign up at anytime you are covered under the group plan based on current employment status. The last eight months of the Special Enrollment Period starts the month after the employment ends or the group health coverage ends, whichever comes first. Medicare.gov/glossary
A set time that a beneficiary can change health plans or return to Original Medicare, such as: you move outside the service area, your Medicare+Choice organization violates its contract with you, the organization does not renew its contract with CMS, or other exceptional conditions determined by CMS. The Special Election Period is different from the Special Enrollment Period (SEP). (See Election Periods; Enrollment; Special Enrollment Period (SEP).)
Guidance for Eligibility, Enrollment and Disenrollment procedures for Medicare Advantage (MA) plans, including MA-PD plans, is provided in Chapter 2 of the Medicare Managed Care Manual. Similar guidance for 1876 Cost plans is provided in Chapter 17, Subpart D of the same manual. .. http://www.cms.hhs.gov
.. CMS provides instructions for enrolling Medicare beneficiaries in Medicare Prescription Drug Plans (PDP's) in the Agency's PDP Guidance for Eligibility, Enrollment and Disenrollment. .. http://www.cms.hhs.gov/