Losing employer coverage or retiring? Start here.
If you delayed Medicare Part B because you or your spouse had qualifying employer coverage, losing that coverage may give you a Special Enrollment Period to sign up for Part B without waiting for the General Enrollment Period.
The timing rules depend on your specific situation, so it is important to confirm when your employer coverage ends, when you want Medicare to begin, and whether you need Medicare Advantage, Medicare Supplement, or Part D coverage after Part B starts.
- Retiring and leaving employer coverage
- Losing coverage through a spouse's employer
- Delaying Part B while actively working
- Moving from employer insurance to Medicare
- COBRA beginning after active employer coverage ends
Initial Enrollment Period (IEP)
Your IEP is the 7-month window when you first become eligible for Medicare, typically around your 65th birthday. It begins 3 months before the month you turn 65, includes your birthday month, and ends 3 months after.
If you're already collecting Social Security at 65, you'll be enrolled in Parts A and B automatically. If not, you need to actively sign up at ssa.gov/medicare.
During your Initial Enrollment Period, you can also review your options for Medicare Advantage, Part D prescription coverage, and Medicare Supplement (Medigap), depending on your eligibility and timing.
See our turning-65 guide for a full timeline of what to do during your IEP.
Medicare Open Enrollment (AEP): October 15–December 7
The AEP runs October 15 to December 7 every year. This is the main annual window for everyone on Medicare to make plan changes for the following calendar year. New coverage starts January 1.
During AEP, you can:
- Switch from Original Medicare to a Medicare Advantage plan (or vice versa)
- Switch from one Medicare Advantage plan to another
- Join, drop, or switch a Part D prescription drug plan
AEP is when carriers release their plan changes for the next year, new premiums, formulary updates, network changes. It's a good idea to review your current plan's Annual Notice of Change each fall, even if you don't plan to switch.
Not sure what to do this fall? Answer a question or two in our Medicare Open Enrollment checklist to get a step-by-step plan for your coverage.
Medicare Advantage Open Enrollment Period (OEP)
The MA OEP runs January 1 to March 31 every year.
This period is only for people already enrolled in Medicare Advantage.
During OEP you can make one change:
- Switch from one Medicare Advantage plan to another
- Drop your Medicare Advantage plan and return to Original Medicare (and add a stand-alone Part D plan)
You cannot use the MA OEP to switch from Original Medicare into a Medicare Advantage plan, that has to happen during AEP or a Special Enrollment Period.
General Enrollment Period (GEP)
The GEP runs January 1 to March 31 every year. It's an enrollment period for people who missed their Initial Enrollment Period and do not qualify for a Special Enrollment Period.
Coverage for those enrolling during GEP starts the month after enrollment. If you're using the GEP because you missed your IEP without creditable coverage, you may owe a Part B late-enrollment penalty for the time you went without, added to your premium for as long as you have Medicare.
Special Enrollment Periods (SEPs)
SEPs let you make plan changes outside the normal windows when something qualifying happens. Common triggers:
- Losing employer or union coverage
- Retiring after delaying Part B
- Losing coverage through a spouse
- Moving outside your plan's service area
- Losing Medicaid
- Certain plan or contract changes
- Certain exceptional circumstances
- Qualifying for Medicaid or for Extra Help with prescription costs
- Becoming eligible for a Medicare Savings Program
- Leaving incarceration
Each Special Enrollment Period has its own eligibility and timing rules. The enrollment window can vary significantly depending on the qualifying event, so it is important to confirm the rules for your specific situation. A licensed agent can confirm whether your situation qualifies and help you act in time.
Delayed Part B because you were still working?
If you delayed Part B while covered by a qualifying employer health plan based on current employment, you may be able to enroll later through a Special Enrollment Period without a Part B late-enrollment penalty.
COBRA and retiree coverage do not always work the same way as active employer coverage for Part B enrollment timing, so do not assume they extend the same protections.
Medicare Supplement (Medigap) Open Enrollment Period
This is a one-time 6-month window that starts the first month you're both age 65 or older and enrolled in Part B. During this window, you can buy any Medigap policy sold in your state with no medical underwriting or denials, and insurers generally cannot charge you more because of pre-existing health problems during this federal open enrollment period.
This is generally the strongest time to compare Medicare Supplement coverage because you have important federal enrollment protections. Outside this window, and outside specific guaranteed-issue Special Enrollment situations, insurers in most states can use medical underwriting, which can mean denial or higher premiums based on health.
See our Medicare Supplement guide for details on the lettered plans and how Medigap works.
Quick Reference: Which Medicare Enrollment Period Might Apply?
- Turning 65 → Initial Enrollment Period
- Already on Medicare and changing plans in fall → Medicare Open Enrollment
- Already in Medicare Advantage Jan–Mar → MA Open Enrollment
- Missed Part B and no SEP → General Enrollment Period
- Retiring/losing qualifying coverage → possible Special Enrollment Period
- Newly 65+ and on Part B → Medicare Supplement Open Enrollment