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Understanding Enrollment Periods (AEP, OEP, IEP, SEP) 

This article explains the CMS-defined enrollment periods that allow beneficiaries to enroll in, switch, or disenroll from Medicare Advantage Prescription Drug (MAPD) plans. 

Annual Election Period (AEP)

Dates: October 15 – December 7

AEP is the main time when Medicare beneficiaries can review and change their MAPD plan for the upcoming year.

During AEP, beneficiaries may:

  • Enroll in a MAPD plan

  • Switch from one MAPD plan to another

  • Disenroll from MAPD and return to Original Medicare

Effective Date:
All AEP changes take effect on January 1 of the next year.

Agent Notes:

  • Only CMS-approved materials for the upcoming plan year may be used.

  • All communication must follow CMS marketing and compliance rules.

Medicare Advantage Open Enrollment Period (OEP)

Dates: January 1 – March 31

OEP allows individuals who are already in a Medicare Advantage or MAPD plan to make a one-time change.

During OEP, a beneficiary may:

  • Switch from one MAPD plan to another

  • Switch from MAPD back to Original Medicare

Important OEP Guidelines:

  • OEP cannot be used to join a MAPD plan for the first time.

  • OEP cannot be advertised or promoted. Agents may only discuss OEP if the beneficiary initiates the conversation.

  • Only one enrollment change is permitted during OEP.

Effective Date:
Changes generally take effect on the first day of the month after the enrollment request.

Initial Enrollment Period (IEP)

IEP is the first time a beneficiary becomes eligible to enroll in a MAPD plan.

A beneficiary may enroll in MAPD during IEP if:

  • They have Medicare Part A and Part B

  • They live in the MAPD plan’s service area

IEP for Individuals Turning 65

A seven-month window:

  • Starts three months before the beneficiary’s 65th birthday month

  • Includes the birth month

  • Ends three months after the birth month

MAPD effective dates depend on when the request is submitted within this window.

IEP for Individuals First Enrolling in Part B After Age 65 (IEP2)

For individuals who delayed Part B:

  • Starts three months before the Part B effective date

  • Includes the Part B start month

  • Ends three months after the start month

This provides a one-time MAPD enrollment opportunity linked to Part B activation.

Special Enrollment Periods (SEPs)

SEPs allow beneficiaries to make MAPD enrollment changes outside of AEP, OEP, or IEP when certain qualifying events occur.

Common MAPD SEPs include:

  • Moving into, out of, or within a MAPD service area

  • Losing certain types of health coverage (e.g., employer or union coverage)

  • Gaining or losing eligibility for Medicaid or certain low-income programs

  • Entering, residing in, or leaving certain institutional settings

  • Becoming eligible for a Chronic Condition Special Needs Plan (C-SNP)

  • Plan non-renewal or plan termination

SEP Effective Dates:
Most SEP elections take effect on the first day of the month after the enrollment request, unless CMS specifies otherwise.

Agents must document the correct SEP and ensure the beneficiary qualifies.

Agent Compliance Guidance

Agents must:

  • Confirm that the beneficiary is eligible for the enrollment period being used

  • Document SEP usage when required

  • Use only CMS-approved MAPD marketing materials

  • Ensure the beneficiary understands their options

  • Follow CMS marketing and communication guidelines

  • Avoid submitting MAPD enrollments outside a valid election period

When to Contact Broker Support

Contact Broker Support if you need assistance with:

  • Confirming the correct enrollment period

  • SEP eligibility

  • MAPD effective dates

  • Service area questions

  • Complex beneficiary scenarios