State of Franklin Insurance • Serving Tennessee since 1987(423) 282-1093  •  sfis@email.com
State of Franklin Insurance
Home / Enrollment Periods
Timing matters

Medicare enrollment periods & Special Enrollment Periods

“Open Enrollment” is not one single rule. Different enrollment windows apply to Parts A/B, Medicare Advantage, Part D, and Medigap.

First distinction: signing up for Medicare Part A or Part B is governed by different rules from joining or changing a Medicare Advantage or Part D plan. Medigap has its own enrollment protections as well.

Part A & Part B enrollment

Initial Enrollment Period
Usually 7 months. It begins 3 months before the month you turn 65, includes your birthday month, and ends 3 months after. If your birthday is on the first day of a month, the timing shifts earlier. Coverage start dates depend on when you enroll.
General Enrollment Period
January 1–March 31 each year. This is for people who need to sign up for Part B (and/or premium Part A) and do not qualify for another enrollment opportunity. Coverage generally starts the month after you enroll. A late-enrollment penalty may apply.
Part B SEP for active employer coverage
If you delayed Part B because you or your spouse had qualifying employer group health coverage based on current employment, you may be able to enroll while that coverage continues or during an 8-month Special Enrollment Period after the employment or job-based coverage ends, whichever comes first.
COBRA warning: COBRA does not extend the 8-month Part B Special Enrollment Period. The clock can start when current employment or job-based coverage ends even if you elect COBRA.

Medicare Advantage & Part D plan enrollment

Initial Enrollment Period
When you are new to Medicare, you can generally join a Medicare Advantage plan or Part D plan during your initial enrollment window. Medicare Advantage requires both Part A and Part B; a stand-alone Part D plan generally requires Part A and/or Part B.
Medicare Open Enrollment (AEP)
October 15–December 7. You can join, switch or drop Medicare Advantage or Part D coverage and switch between Original Medicare and Medicare Advantage. Changes generally take effect January 1.
Medicare Advantage Open Enrollment
January 1–March 31. If you are already in a Medicare Advantage plan, you can make one change: switch to another Medicare Advantage plan or return to Original Medicare and, if needed, join a stand-alone Part D plan. This period does not allow someone in Original Medicare to join Medicare Advantage.

Medigap Open Enrollment is different

Your federal Medigap Open Enrollment Period is generally a one-time six-month period that starts the first month you are 65 or older and enrolled in Part B. During this period, you can buy any Medigap policy sold in your state without being denied because of pre-existing health problems.

It does not repeat every fall. After it ends, medical underwriting may apply unless you qualify for a guaranteed-issue right or another protection.

Common Special Enrollment Period situations

Special Enrollment Periods (SEPs) allow changes outside normal enrollment windows after certain life events. The exact actions and timing depend on the event, so the examples below are a guide—not a substitute for checking the specific Medicare rule.

You move

Moving outside your plan's service area, moving to an area with new plan options, or certain moves involving institutions can create an SEP.

You lose other coverage

Losing employer/union coverage or other qualifying coverage may create an enrollment opportunity. The rules for Part B and for MA/Part D are not identical.

Medicaid or Extra Help changes

Gaining, losing or changing Medicaid/Extra Help status can create special opportunities to change drug or Medicare Advantage coverage. Current rules can permit more frequent changes in certain situations.

Plan or contract changes

If a plan leaves Medicare, terminates its contract, or changes service availability, affected members may receive a special opportunity to choose new coverage.

Institutional changes

Moving into, residing in, or moving out of certain institutions can create additional election rights.

5-star Special Enrollment Period

If a 5-star Medicare Advantage or Part D plan is available in your area, Medicare provides a special opportunity to switch to a 5-star plan. It can generally be used once between December 8 and November 30 of the following year.

SEP does not always mean “any change you want”

Some SEPs allow only specific actions. For example, an SEP may permit joining a certain type of plan, switching plans, or returning to Original Medicare, but not every combination. Before using an SEP, confirm:

  • The event that triggered it
  • The exact start and end dates
  • What changes are permitted
  • When the new coverage starts
  • Whether drug coverage or Medigap needs separate action
Medigap warning: Being allowed to leave Medicare Advantage does not automatically guarantee that you can buy any Medigap plan you want. Guaranteed-issue and trial-right rules are separate and should be checked before you cancel existing coverage.

Official Medicare resources

Medicare rules can change. These pages were written from current Medicare.gov guidance and should be reviewed periodically.

Call Mike • (423) 282-1093