Your Initial Enrollment Period
Your Initial Enrollment Period (IEP) is a 7-month window centered on your 65th birthday month:
- 3 months before your 65th birthday month
- Your 65th birthday month
- 3 months after your 65th birthday month
You can enroll in Parts A, B, C, D, and Medigap during this window. Use our free IEP date calculator to find your exact dates.
When coverage starts
- Enroll in the 3 months before your birthday month → coverage starts the first of your birthday month
- Enroll during your birthday month → coverage starts the following month
- Enroll in the 3 months after → coverage starts 2-3 months later
For coverage on time, enroll before your birthday month.
If you're already receiving Social Security
If you started Social Security or Railroad Retirement Board benefits before 65, you're automatically enrolled in Parts A and B starting the first of your 65th birthday month. You'll receive your Medicare card in the mail about 3 months before your 65th birthday. You can decline Part B (return the card) if you have other creditable coverage, but Part A is automatic.
If you're working past 65
If you have creditable employer coverage from a company with 20+ employees, you can delay Part B enrollment without penalty. When that coverage ends, you get an 8-month Special Enrollment Period to enroll in Part B. See our Working past 65 guide.
The Annual Enrollment Period
Once you're already in Medicare, the Annual Enrollment Period (AEP) runs October 15 through December 7 each year. During AEP, you can:
- Switch from Original Medicare to Medicare Advantage
- Switch from Medicare Advantage back to Original Medicare
- Switch between Medicare Advantage plans
- Enroll in, switch, or drop a standalone Part D plan
Changes take effect January 1 of the next year.
Medicare Advantage Open Enrollment
From January 1 through March 31, current Medicare Advantage members can switch MA plans once or drop back to Original Medicare with a Part D plan. You cannot use MA-OEP to switch into MA from Original Medicare.
General Enrollment Period
From January 1 through March 31, anyone who missed their IEP and doesn't have other creditable coverage can sign up for Parts A and B. Coverage starts the first of the month after enrollment. Late enrollment penalties usually apply.
Special Enrollment Periods
Triggered by qualifying life events: moving, losing employer coverage, plan non-renewal, qualifying for Extra Help/Medicaid, and others. SEPs let you make Medicare changes outside the usual windows.
The 6-month Medigap window
Ohio's most consequential enrollment window: your Medigap Open Enrollment Period. Six months starting the month you're 65 and enrolled in Part B. During this window, Ohio Medigap insurers must sell you any policy at the best rate regardless of health history. After it closes, Ohio underwriting applies — insurers can decline you, charge more, or exclude pre-existing conditions.
What happens if you miss your IEP
- You wait for the General Enrollment Period (January 1 – March 31)
- You face a Part B late enrollment penalty: 10% added to your premium for every 12-month period you could have had Part B but didn't. This penalty lasts as long as you have Part B.
- You may face a Part D late enrollment penalty: about 1% of the national base premium for every month without creditable drug coverage. Permanent.
- You may have a gap in coverage
If you missed your IEP and have a life-changing event (move, loss of employer coverage), you may qualify for a Special Enrollment Period that lets you enroll without the late penalty.