How to Enroll in Medicare
Understanding enrollment periods and deadlines is critical — missing them can result in permanent late enrollment penalties and gaps in coverage.
Automatic Enrollment — Are You Already Enrolled?
You will be automatically enrolled in Medicare Parts A and B if you are already collecting Social Security retirement or disability benefits before age 65. Your Medicare card will be mailed to you about 3 months before your 65th birthday (or your 25th month of SSDI).
If you are not receiving Social Security benefits yet, you will need to actively enroll during your Initial Enrollment Period. Many people who continue working past 65 intentionally delay Part B enrollment to avoid the premium while covered by their employer's plan.
Medicare Enrollment Periods
There are several enrollment periods for Medicare. Knowing which one applies to you is essential.
Initial Enrollment Period (IEP)
Your first chance to enroll — applies to most people turning 65
- Enroll in Parts A and B during this 7-month window
- If you enroll in the 3 months before your birthday month, coverage starts the 1st of your birthday month
- If you enroll in your birthday month or after, there may be a delay in Part B start date
- Also your window to enroll in a Part D drug plan or Medicare Advantage plan
Delaying enrollment beyond your IEP without qualifying coverage can result in permanent late enrollment penalties for Part B (10% per 12 months delayed) and Part D (1% per month delayed).
Special Enrollment Period (SEP)
For people who delayed enrollment due to employer group health coverage
- Available if you have (or had) coverage through your own or your spouse's current employer
- Must be active employment — COBRA and retiree coverage do NOT qualify
- No late enrollment penalty if you enroll during your SEP
- You have 8 months from when employment or coverage ends
- Part D SEP: 2 months after creditable drug coverage ends
COBRA and retiree insurance are NOT considered creditable coverage for avoiding late enrollment penalties. Enroll in Medicare when you leave active employer coverage.
General Enrollment Period (GEP)
Annual window if you missed your IEP and don't qualify for a SEP
- Open to anyone who did not enroll during their IEP and doesn't have a SEP
- Coverage begins July 1 of that year — a 3–6 month gap is possible
- Late enrollment penalties will apply for Part B and Part D
Annual Enrollment Period (AEP)
Change your Medicare Advantage or Part D plan each fall
- Switch from Original Medicare to Medicare Advantage (or vice versa)
- Change from one Medicare Advantage plan to another
- Join, drop, or switch a Part D prescription drug plan
- Review your current plan's changes for the upcoming year during this period
Medicare Advantage Open Enrollment Period (OEP)
A second chance to make one plan change early in the year
- Only available if you are already enrolled in a Medicare Advantage plan
- Switch to a different Medicare Advantage plan
- Switch back to Original Medicare (and add a standalone Part D plan)
- Cannot be used to switch from Original Medicare to Medicare Advantage
Step-by-Step Enrollment Guide
Follow these steps to enroll in Medicare the right way.
Confirm Your Eligibility
You are eligible for Medicare at age 65 if you are a U.S. citizen or permanent legal resident who has lived in the U.S. for at least 5 years. You may also be eligible under 65 if you have received Social Security Disability Income (SSDI) for 24 months, have End-Stage Renal Disease (ESRD), or have ALS (Lou Gehrig's disease).
Determine Your Enrollment Window
Check which enrollment period applies to you based on your age, current insurance coverage, and employment status. Your Initial Enrollment Period begins 3 months before the month you turn 65. If you are still working with employer coverage, you may qualify for a Special Enrollment Period.
Check for Automatic Enrollment
If you are already receiving Social Security benefits at least 4 months before age 65, you will be automatically enrolled in Medicare Parts A and B. Your Medicare card will arrive in the mail 3 months before your 65th birthday. Review the card and decide whether to keep Part B or defer it if you have active employer coverage.
Enroll Online, by Phone, or in Person
If you are not automatically enrolled: (1) Online at ssa.gov — this is the easiest method; (2) By phone at 1-800-772-1213; or (3) Visit your local Social Security Administration office. Applying for Part A only: ssa.gov/benefits/medicare. For Medicare Advantage or Part D, enroll directly through a private plan.
Choose Additional Coverage
Original Medicare (Parts A + B) alone has no out-of-pocket maximum. Consider adding a Medigap Supplement plan to cover the 20% coinsurance and other gaps, OR enroll in a Medicare Advantage (Part C) plan. Also consider a standalone Part D plan if you choose Original Medicare.
Compare Plans with a Licensed Agent
There are many Medicare Advantage and Medigap plans available — and they vary significantly in cost, coverage, and network. A licensed agent like David Marsh can compare plans at no cost to you and help ensure you find the best fit for your health needs and budget.
Navigating Enrollment Alone Can Be Risky
Missing a deadline can cost you thousands of dollars in permanent penalties. David Marsh helps you identify the right enrollment period and guides you through the entire process at no cost.