Initial Coverage Election Period (ICEP) Also called IEP and PDP
The three months immediately before you are entitled to Medicare Part A and enrolled in Part B. If you choose to join a Medicare health plan during your Initial Coverage Election Period, the plan must accept you. The only time a plan can deny your enrollment during this period is when it has reached its member limit set by Medicare.
 

Annual Election Period (AEP) Starting 2011 is October 15 to December 7th.
This is also called Open Enrollment Period and so can very confusing as the next period is also call OEP
The Annual Election Period runs from November 15 through December 31 each year.  During this time, AEP, Medicare beneficiaries may change prescription drug plans, change Medicare Advantage plans, return to original Medicare, or enroll in a Medicare Advantage plan for the first time.  Enrollment changes take effect on January 1.

Medicare beneficiaries may not add or drop Part D drug coverage during the Open Enrollment Period.  Those who already have drug coverage can only change to another option with drug coverage.  Those who do not have drug coverage may not change to an option that provides drug coverage.  Permissible changes during the Open Enrollment Period include:
 

	Medicare Advantage Prescription Drug Plan (MA-PD) to a different MA-PD
	MA-PD to Original Medicare and a Part D Prescription Drug Plan (PDP)
	Original Medicare and a PDP to an MA-PD
	Medicare Advantage Only (MA-only) plan to a different MA-only plan
	MA-only plan to original Medicare
	Original Medicare to an MA-only plan

Beneficiaries who want to use the Open Enrollment Period to return to Original Medicare from an MA-PD must do so by enrolling in a Part D Prescription Drug Plan (PDP).  Enrollment in a PDP during either the Annual Election Period or the Open Enrollment Period terminates enrollment in a Medicare Advantage plan. Because beneficiaries are generally limited to changing their prescription drug coverage during the Annual Election Period, Medicare Advantage Plan (MA-PD) enrollees who want to return to Original Medicare during the Open Enrollment Period have a Part D Special Enrollment Period that allows them to make one enrollment into a PDP.
 

Someone who enrolls in Part B during the General Enrollment Period also has a Special Enrollment Period (SEP) for Part D.  From April through June of each year a new Part B enrollee may make one election to join a Part D plan. Because beneficiaries who only have Part A and not Part B are not eligible to enroll in a Medicare Advantage plan, the SEP enables beneficiaries who elect Part B during the General Enrollment Period to enroll in a Medicare Advantage plan with drug coverage (MA-PD).
 

SEP - Special Election Period.  Can be at anytime depending on circumstances. It is best to discuss your particular situation.
You may qualify for a Special Enrollment Period if you:

	Are enrolled in a Medicare Advantage Prescription Drug (MA-PD) plan and leave that plan to enroll in Original Medicare plus a Medicare prescription drug plan during the Medicare Advantage Plans Open Enrollment Period. This enrollment period runs January 1 through March 31 each year.
	Move permanently outside your plan’s service area.
	Have a low-income subsidy. People with lower incomes can get extra help. Premiums may be reduced or eliminated, and other payments may be less. If you qualify for a low-income subsidy, the late enrollment penalty does not apply.
	Have enrolled in another prescription drug plan or a Medicare Advantage plan whose contract is terminated.
	Are not adequately informed about creditable prescription drug coverage.
	Lose your previous creditable coverage through no action of your own.
	Have been enrolled or disenrolled by the error of a Federal employee or a contractor hired by the Federal government.
	Were eligible for both Medicare and Medicaid ("dual eligible") but lost your dual eligibility status.
	Want to move from an employer group or union-sponsored prescription drug plan to a Medicare Prescription Drug Plan during that group’s open enrollment period.
	Want to leave your current Medicare Prescription Drug Plan because the Federal government has determined the plan violated a material provision of its Medicare contract in relation to services provided to you.
	Are enrolled in a Plan that isn’t renewing its contract with Medicare.
	Want to move from a Program of All-Inclusive Care for the Elderly (PACE) to a Medicare Prescription Drug Plan.
	Live in or you are moving in or out of a skilled nursing facility, nursing facility, intermediate care facility for the mentally retarded, psychiatric hospital or unit, rehabilitation hospital or unit, long-term care hospital or swing-bed hospital.
	Have a Medicare entitlement determination that is made retroactively.
	Are not eligible for premium-free Part A and enroll in Medicare Part B during the January – March 2009 Part B General Enrollment Period.
	Qualify for other special enrollment periods that may be authorized by the Federal government.

Lockin - April 1 to December 31st.  This is the period when you keep what you chose.