Medicare Enrollment Periods: When You Can Sign Up and Make Changes

Medicare has specific windows of time when you can enroll in coverage or make changes to your plan. If you miss your enrollment window, you may face penalties or have to wait until the next enrollment period to make changes. Understanding these deadlines is one of the most important parts of navigating Medicare.

This guide breaks down every enrollment period so you know exactly when you can sign up and what happens if you miss a deadline.

Initial Enrollment Period (IEP)

Your Initial Enrollment Period is a critical window that happens only once when you first become eligible for Medicare. It's a 7-month period centered around your 65th birthday, and it's the easiest time to enroll without restrictions.

The IEP Timeline

Your IEP begins 3 months before your birthday month and extends 3 months after your birthday month. Here's the month-by-month breakdown:

Annual Enrollment Period (AEP)

After your Initial Enrollment Period ends, the Annual Enrollment Period (AEP) is your yearly opportunity to make changes to your Medicare coverage. This is when most beneficiaries review and adjust their plans.

AEP Dates

October 15 through December 7 every year. Changes made during AEP take effect January 1 of the following year.

What You Can Do During AEP

• Switch from Original Medicare to Medicare Advantage
• Switch from Medicare Advantage to Original Medicare
• Change your Medicare Advantage plan to a different MA plan
• Change your Part D prescription drug plan
• Add or drop coverage

AEP is your main window each year to reassess your coverage and make adjustments if your needs have changed.

Medicare Advantage Open Enrollment Period (MA OEP)

If you're already enrolled in a Medicare Advantage plan, you get an additional enrollment window early in the year.

MA OEP Dates

January 1 through March 31 each year. During this period, if you're in a Medicare Advantage plan, you can:

• Switch to a different Medicare Advantage plan
• Switch back to Original Medicare (with or without a Medigap plan)

Changes made during MA OEP take effect the 1st of the following month.

Special Enrollment Periods (SEP)

If you experience certain qualifying life events, you may be eligible for a Special Enrollment Period outside the regular enrollment windows. These events could include:

Qualifying Life Events

• Job loss: Loss of employer coverage when you turn 65 or older
• Moving: Permanent relocation to a new state or service area
• Loss of other coverage: Medicaid eligibility changes, TRICARE loss, or other health coverage ending
• Marriage: Getting married, which may allow a spouse to enroll
• Divorce: Getting divorced may trigger a 60-day SEP for the divorced spouse
• Death of a spouse: Widows or widowers may have a SEP to make changes
• Leaving a long-term care facility: Discharge from a nursing home or similar facility

If you qualify for a SEP, you typically have 60 days from the qualifying event to make changes. It's important to document your qualifying event and contact Medicare to confirm your eligibility.

Medigap Open Enrollment Period

If you choose Original Medicare, you may want to add a Medigap (Medicare Supplement) policy to help cover costs that Medicare doesn't. Medigap has its own enrollment window.

When It Starts

Your Medigap Open Enrollment Period is a one-time, 6-month window that begins the month you turn 65 and are enrolled in Part B. During this period, insurance companies cannot deny you coverage or charge you more based on pre-existing health conditions.

Why It Matters

This is the only time you may be able to buy Medigap coverage at standard rates without medical underwriting. If you miss this window and want to buy Medigap later, the insurance company can review your health history and may deny you coverage or charge you higher premiums.

Part D (Prescription Drug) Enrollment

Part D prescription drug coverage has the same basic enrollment windows as Medicare generally:

• During your IEP: When you first become eligible for Medicare
• During AEP: October 15 to December 7 each year
• During a SEP: If you qualify for a Special Enrollment Period

Part D enrollment is particularly important because it has its own late enrollment penalty.

Late Enrollment Penalties

If you miss your enrollment windows and don't enroll when you're first eligible, Medicare may impose penalties that could last the rest of your life.

Part B Late Enrollment Penalty

If you don't enroll in Part B when you're first eligible (during your IEP), your monthly Part B premium increases by 10% for each full 12-month period you were eligible but didn't enroll. This penalty applies for as long as you have Part B coverage.

Part D Late Enrollment Penalty

If you go 63 or more days without Part D coverage after you first become eligible, you'll pay a penalty. The penalty is based on how long you went without coverage and is added to your monthly Part D premium indefinitely.

What Doesn't Trigger Penalties

If you had qualifying coverage (such as employer or union coverage, TRICARE, or Medicaid) that was at least as good as Part B or Part D, you generally won't face penalties for enrolling late when that coverage ends. Keep records of any prior coverage to prove you had creditable coverage.

A Helpful Checklist for Enrollment Deadlines

Key Takeaways

Medicare enrollment windows are strict. Here's what you need to remember:

• Your Initial Enrollment Period is a one-time, 7-month window around your 65th birthday. Use it wisely.
• The Annual Enrollment Period (October 15 - December 7) is your yearly chance to review and adjust your coverage.
• Medigap has a one-time, 6-month window starting when you turn 65 and enroll in Part B.
• Missing deadlines can result in permanent penalties on your Part B and Part D premiums.
• Special Enrollment Periods may be available if you have qualifying life events.
• Keep records of any prior health coverage that was creditable to avoid penalties.

For more details on enrollment deadlines and your specific situation, visit Medicare.gov or speak with a licensed insurance advisor who can review your individual circumstances. Learn more about your coverage options in our guide to Medicare Advantage vs. Medigap.