The two enrollment timelines that matter

Two different windows kick off when you turn 65:

• Initial Enrollment Period (IEP) for Medicare itself — a 7-month window: 3 months before your birth month, your birth month, and 3 months after. This is when you enroll in Parts A and B.
• Medigap Open Enrollment Period — a 6-month window starting the month you have BOTH Part B AND are 65. During this window, no Medigap insurer can deny you for health reasons. Outside this window, in most states they can.

Miss the IEP, you face permanent late-enrollment penalties on Part B and Part D. Miss the Medigap Open Enrollment, you may not be able to get Medigap later if your health has changed.

Step-by-step checklist

📅 6 months before your 65th birthday

• [ ] Confirm your Social Security records are accurate (correct birth date, employment history). Sign up at ssa.gov if you haven't already.
• [ ] If you're working past 65 with employer coverage, ask HR for a "Notice of Creditable Coverage" letter. You'll need this to avoid late-enrollment penalties when you eventually do enroll.
• [ ] Decide if your employer coverage is "primary" or "secondary" once Medicare becomes available. (Companies with 20+ employees: employer coverage stays primary; companies under 20: Medicare becomes primary.)
• [ ] If you're NOT working with employer coverage, mark your calendar 3 months before your birth month — that's when your IEP starts.

📅 3 months before your 65th birthday — IEP starts

• [ ] Enroll in Medicare Part A (hospital). Most people pay no premium for Part A — go ahead and enroll even if you're keeping employer coverage.
• [ ] Decide whether to enroll in Part B now (recommended for most people) OR delay.
• [ ] If you're delaying Part B because you have employer coverage, document everything in writing. The "creditable coverage" letter is your proof.
• [ ] Start researching Medicare Supplement (Medigap) and Medicare Advantage options for when you do enroll. Compare your options →
• [ ] If you're considering Part D (prescription drugs), make a complete list of every medication you take. We'll use this to compare plan formularies.

📅 Your birth month

• [ ] If you enrolled in Part B at the start of your IEP, coverage begins the first day of your birth month.
• [ ] Pick your supplemental coverage path: Original Medicare + Medigap + Part D, OR Medicare Advantage. Book a free call if you want help comparing.
• [ ] Enroll in your supplemental plan. Coverage typically starts the first of the month after enrollment.

📅 3 months after your birth month — IEP ends

• [ ] Final chance to enroll in Part B without penalty (unless you have qualifying employer coverage).
• [ ] Final chance to enroll in Part D without penalty (unless you have creditable drug coverage from another source).
• [ ] Final chance for guaranteed-issue Medigap (some plans tie this to IEP-end + 6 months for the Medigap Open Enrollment Period).

📅 If you're delaying Part B due to employer coverage

You have a Special Enrollment Period (SEP) that runs for 8 months after your employer coverage ends. Enroll in Part B during that window and you avoid late-enrollment penalties. Critical: this SEP ends 8 months after employer coverage stops — gap insurance like COBRA does NOT extend it.

• [ ] When you stop working or lose employer coverage: enroll in Part B within 8 months
• [ ] At the same time: enroll in Part D within 63 days to avoid Part D late-enrollment penalty
• [ ] Pick your supplemental coverage (Medigap or Medicare Advantage) — your Medigap Open Enrollment Period also kicks off when you enroll in Part B (if you're 65+)

What to bring to your enrollment

• Social Security card (and your spouse's, if relevant)
• Driver's license
• Bank account info (for premium auto-deduction)
• Medicare card (you'll get this in the mail before your IEP starts; keep it safe)
• List of current medications + dosages
• List of current doctors + specialists
• Recent insurance card (for coordination of benefits)

The penalties you can't undo

• Part B late enrollment penalty: 10% of your Part B premium for every full 12-month period you could have had Part B but didn't. Permanent — for as long as you have Part B (often the rest of your life).
• Part D late enrollment penalty: 1% of the national base beneficiary premium for every month you went without creditable drug coverage. Permanent.
• Medigap medical underwriting: outside your one-time Medigap Open Enrollment Period, insurers in most states can deny you or charge more if you have health issues. Hard to undo if you delay too long.

Common mistakes

• Assuming Medicare = free. Part A is free for most. Part B has a premium. Most people add at least one supplemental plan. Total monthly cost varies $175-$400+/month depending on your choices.
• Picking the cheapest Part D plan. The cheapest Part D plan on paper is rarely the cheapest one for YOUR specific medications. Always run your meds through Medicare's Plan Finder before choosing.
• Skipping Part D because you don't take prescriptions yet. The late enrollment penalty is permanent. Enroll in a low-cost Part D plan even if you don't currently need it.
• Picking based on a TV commercial or a friend's recommendation. Your doctors, your prescriptions, your travel pattern — none of those match the person in the commercial or your friend.

Get personalized help

Two free options to dig into your specific situation:

Related: Medicare 101 overview · Late enrollment penalty deep-dive · Advantage vs Medigap