IRMAA Basics
Comprehensive Guide to Medicare Enrollment Periods
Verified against SSA POMS as of September 20, 2026
The short answer
Medicare Enrollment Periods include the Initial Enrollment Period (IEP) that varies based on eligibility, the Annual Election Period (AEP) typically from October 15 to December 7, and Special Enrollment Periods (SEP) for qualifying life events. Each period has specific conditions and effective dates that guide enrollment eligibility. Medicare.gov is the most comprehensive source for rules surrounding enrollment periods.
Initial Enrollment Period (IEP)
The Initial Enrollment Period (IEP) for Medicare Parts A, B, and D is a seven-month window. It begins three months before the month an individual first becomes eligible for Medicare, includes the month of eligibility, and ends three months after. This period is crucial for enrolling in Medicare to ensure coverage starts promptly.
CMSPDF:medicare/eligibility-and-enrollment/medicaremangcareeligenrol/downloads/finalmaenrollmentanddisenrollmentguidanceupdateforcy2012-rev11162011.pdf View source ›Annual Election Period (AEP)
The Annual Election Period (AEP), usually takes place between October 15 and December 7 each year, allowing individuals to enroll, drop, or switch plans.
CMSPDF:medicare/eligibility-and-enrollment/medicarepresdrugeligenrol/downloads/finalpdpenrollmentanddisenrollmentguidanceupdateforcy2012-rev11162011.pdf View source ›Special Enrollment Periods (SEP)
Special Enrollment Periods (SEP) occur due to qualifying events such as changes in residence, loss or change of health coverage, changes in government financial assistance, plan performance and contract status, and exceptional or special circumstances. Each specific SEP may have different coverage effective dates depending on the qualifying event.
CMSPDF:medicare/prescription-drug-coverage/prescriptiondrugcovcontra/downloads/-pdp_enrollmentguidance%20exhibits_sep082006.pdf View source ›Effective Dates
Enrollment periods have specific effective dates, crucial for ensuring continuous coverage. For individuals gaining Medicare eligibility due to age, the Initial Enrollment Period (IEP) is a 7-month window. This period begins 3 months before the individual's birthday month, includes the birthday month, and extends 3 months after the birthday month. For example, a person turning 65 in April will have an IEP from January through July.
CMSPDF:medicare/eligibility-and-enrollment/medicaremangcareeligenrol/downloads/final_ma_enrollment_and_disenrollment_guidance_update_for_cy2012_-_revised_872012_for_gy2013_v3.pdfFrequently asked
When is the Medicare Annual Election Period?
The Medicare Annual Election Period is typically held from October 15 to December 7 each year.
What qualifies for a Special Enrollment Period?
A Special Enrollment Period may be triggered by events such as moving to a new area, losing other insurance coverage, or eligibility changes.
How long is the Initial Enrollment Period for Medicare?
The Initial Enrollment Period lasts for seven months, starting three months before the month of Medicare eligibility and ending three months after.
Can I change my Medicare plan outside of the Annual Election Period?
Yes, under certain conditions that qualify for a Special Enrollment Period, you can change your plan outside the Annual Election Period.