Your turning-65 window, called the Initial Enrollment Period, is a one-time 7-month window to sign up for Part A and Part B. It starts 3 months before the month you turn 65 and ends 3 months after it. Medicare Open Enrollment, October 15 to December 7 every year, is for people who already have Medicare to change their Medicare Advantage or Part D plan, with changes starting January 1. Mixing up the two is one of the most common and costly Medicare mistakes. This comparison shows how each window works.
What is the turning-65 enrollment window?
The Initial Enrollment Period is your first chance to sign up for Medicare. Medicare.gov explains it on its page about when Medicare coverage starts: the 7-month period begins 3 months before the month you turn 65, includes your birthday month and ends 3 months after it. If your birthday falls on the first of the month, the window shifts one month earlier.
When you sign up matters for your start date. Sign up during the first 3 months and coverage usually starts the first day of your birthday month. Sign up during your birthday month or later and coverage starts the first day of the month after you sign up. During this window you can also choose a Medicare Advantage plan or a Part D drug plan.
If you already get Social Security retirement benefits when you turn 65, you are usually enrolled in Part A and Part B automatically, and your card arrives in the mail. You still need to act during the same window to choose a Medicare Supplement, a Medicare Advantage plan or a drug plan, because those are never automatic. If you aren't getting Social Security yet, nothing happens until you sign up yourself.
What is Medicare Open Enrollment?
Open Enrollment, often called the Annual Enrollment Period, runs October 15 to December 7 each year. It is for people who already have Medicare. During it you can switch Medicare Advantage plans, move between Medicare Advantage and Original Medicare, and join, switch or drop a Part D plan. Changes take effect January 1. Our page on Medicare Open Enrollment covers the dates and checklist.
Your plan mails an Annual Notice of Change before Open Enrollment begins. That letter is the trigger to review your coverage, because premiums, copays, drug lists and networks can all change for the new year.
Open Enrollment is not a time to sign up for Part B for the first time. If you missed your Initial Enrollment Period and don't qualify for a Special Enrollment Period, the window for Part B is the General Enrollment Period, January 1 to March 31.
How do the two windows compare?
| Question | Initial Enrollment Period | Open Enrollment |
|---|---|---|
| Who it is for | People becoming eligible for Medicare, usually at 65 | People who already have Medicare |
| When | 7 months around your 65th birthday month | October 15 to December 7, every year |
| Sign up for Part A and Part B? | Yes | No |
| Choose or change Medicare Advantage? | Yes, choose a plan | Yes, switch or drop |
| Join or change Part D? | Yes | Yes |
| When coverage starts | Based on the month you sign up | January 1 |
| Risk of missing it | Coverage gap and possible lifelong penalties | Stuck with your current plan for another year, in most cases |
Where does the Medigap window fit?
A third window matters for Medicare Supplement coverage. Your 6-month Medigap Open Enrollment Period starts the first month you are 65 and enrolled in Part B. During it, insurers can't turn you down or charge more because of your health. It happens once and isn't repeated each fall. Annual Open Enrollment doesn't give you a federal right to buy a Medicare Supplement without health questions, which surprises many people who plan to switch from Medicare Advantage later. Our guide to switching from Medicare Advantage to Medigap explains why.
What other windows should I know about?
Two more come up often:
- Medicare Advantage Open Enrollment, January 1 to March 31, lets people already in a Medicare Advantage plan make one change: switch to another Medicare Advantage plan or go back to Original Medicare and join a drug plan. Our page on AEP vs. Medicare Advantage OEP compares them.
- Special Enrollment Periods open when your situation changes, such as losing job-based coverage, moving, or getting Medicaid or Extra Help. If you delayed Part B because you or your spouse were still working, you have 8 months after the job or the coverage ends to sign up. See our guide to Special Enrollment Periods.
What mistakes should I avoid?
- Waiting until October to sign up for Part B at 65. Open Enrollment won't enroll you in Part B.
- Assuming COBRA or retiree coverage lets you delay Part B. It doesn't count as current employment.
- Letting your Medigap window pass while deciding, then facing health questions later.
- Ignoring the Annual Notice of Change each fall and letting a plan renew after its drug list or network changed.
- Forgetting that coverage started late in the Initial Enrollment Period can leave a gap after employer coverage ends.
Are the windows the same in North Carolina, South Carolina and Tennessee?
Yes. These enrollment periods are federal, so the dates are the same whether you live in Charlotte, Indian Land or Nashville. What differs is the set of plans you can choose from in each window, since Medicare Advantage and Part D options vary by county, and some state rules add Medigap rights. If you're turning 65 and moving between states, plan your enrollment around the address where you'll live when coverage starts.
How The Jordan Insurance Agency can help
We start every turning-65 review by putting your exact dates on a calendar: your Initial Enrollment Period, your Medigap window and any Special Enrollment Period from work coverage. Then we compare Medicare Supplement, Medicare Advantage and Part D options so you choose once and choose well. Already on Medicare? We'll review your plan before Open Enrollment closes on December 7. Schedule Your Consultation to review your options.
Reviewed by Billy Jordan Jr., licensed insurance agent · Licensing & Credentials · Last reviewed November 12, 2026 · Sources are linked in the answer above.
Licensing: Billy Jordan Jr. is licensed in 23 states, including North Carolina, South Carolina and Tennessee. See Licensing & Credentials.
Office: North Carolina and South Carolina clients are served by the Charlotte office, 3540 Toringdon Way, Suite 200, Charlotte, NC 28277, (704) 926-7565. Tennessee clients are served by the Nashville office, 159 4th Ave N, Suite 100, Nashville, TN 37219, (615) 558-6082.
Medicare disclaimer: We do not offer every plan available in your area. Currently we represent 8 organizations which offer 91 products in North Carolina, 7 organizations which offer 70 products in South Carolina, and 7 organizations which offer 65 products in Tennessee. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. Read the full Medicare disclaimer.
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