Pick the situation that fits → see your exact 2026 enrollment window.
Starting Part A and Part B is distinct from choosing Medicare Advantage or separate drug coverage. Begin with the official sign-up instructions, then compare coverage options. A plan-shopping deadline should not be substituted for a deadline to start Medicare.
The answer depends on your circumstances and coverage. Confirm the employer coverage rules and coordinate with the benefits administrator before delaying Part B. Retirement, COBRA and active employment should not be treated as interchangeable situations.
Write down the current coverage end date, enrollment period and confirmed effective date. Check official instructions before canceling anything. A planning calendar is useful for organization but cannot grant an enrollment right.
Read the official sign-up guidance for the General Enrollment Period and Special Enrollment Periods. Check whether a specific exception applies, and ask Medicare or Social Security about your situation. Do not assume annual plan Open Enrollment fixes a missed Part B sign-up deadline.
| Item | What it means |
|---|---|
| Start Medicare | Part A and Part B sign-up guidance. |
| Change a plan | Health or drug plan enrollment rules. |
| Special circumstances | Check the specific qualifying event. |
Official sources: Medicare.gov official reference · Medicare.gov official reference
Last reviewed: 2026-10-12 — the added explanation and linked sources only. Existing calculator outputs and earlier content require separate validation. Educational information; not individualized insurance, tax or medical advice.
Quick answer: Your Medicare enrollment window depends on your situation. Most people use their 7-month Initial Enrollment Period (the 3 months before, the month of, and 3 months after your 65th birthday). Others qualify for a Special Enrollment Period — losing employer coverage or moving — while the rest use the General (Jan–Mar) or Annual (Oct 15–Dec 7) windows. Enrolling in the right one avoids permanent late penalties.
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Special Enrollment Periods are where the off-season sales are — but only if you catch them in time. Our SEP & AEP trackers (Excel + Google Sheets) flag every client window automatically so you work the calendar instead of memorizing it.
See the enrollment toolkits for free →| Window | When | What you can do |
|---|---|---|
| Annual Enrollment (AEP) | Oct 15 – Dec 7 | Change anything; effective Jan 1 |
| Medicare Advantage OEP | Jan 1 – Mar 31 | Switch MA plans once, or return to Original Medicare + a Part D plan |
| Initial Enrollment (IEP) | 7 months around your 65th birthday | Enroll for the first time |
| Special Enrollment (SEP) | Triggered by a life event | Varies — usually about 2 months from the event |
October 15 through December 7. Changes you make take effect January 1.
January 1 to March 31. If you're already in a Medicare Advantage plan, you can make one switch — to a different MA plan, or back to Original Medicare with a Part D plan.
Life events such as losing employer coverage, moving out of your plan's area, your plan leaving, or qualifying for Medicaid/Extra Help. Most SEPs last about two months, but the exact rules vary — confirm with Medicare or a licensed agent.