For millions of Americans approaching age 65, enrolling in Medicare is a critical step in planning for healthcare in retirement. While Medicare Part A (hospital insurance) often kicks in automatically for those already receiving Social Security benefits, signing up for Medicare Part B—which covers doctor visits, preventive services, and outpatient care—requires a few more steps.
Medicare can feel like an alphabet soup of choices. Understanding when and how to enroll in Part B helps avoid unnecessary late penalties and ensures your coverage starts when you need it.
Here’s what you need to know about enrolling in Medicare Part B, how much it might cost, and whether it makes sense to enroll at age 65 or delay coverage.
Step-by-Step: How to Enroll in Medicare Part B
If you’ve decided to start Medicare, here’s how to get Part B coverage:
- Confirm Eligibility
You’re eligible for Medicare Part B if:
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- You’re age 65 or older and a U.S. citizen or legal resident, or
- You’re under 65 with a qualifying disability and have received Social Security disability benefits for 24 months.
- You’re age 65 or older and a U.S. citizen or legal resident, or
If you’re already receiving Social Security benefits, you may have been automatically enrolled in Part A, but Part B requires active enrollment unless you opted in earlier
- Understand Your Enrollment Window
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- Initial Enrollment Period (IEP): This 7-month window starts three months before your 65th birthday, includes your birth month, and extends three months after.
- Special Enrollment Period (SEP): If you delayed Medicare because you had employer coverage, you may qualify for an 8-month SEP that begins when employment or employer-based insurance ends—whichever comes first.
- Initial Enrollment Period (IEP): This 7-month window starts three months before your 65th birthday, includes your birth month, and extends three months after.
Important: Employer-sponsored retiree coverage or COBRA does not count as creditable coverage for delaying Part B. Failing to enroll when required could result in a 10% penalty for each full 12-month period you could have had Part B but didn’t sign up (and weren’t covered by a group health plan based on current employment).
This penalty is added to your premium for as long as you have Part B.
- Complete Required Forms
If you’re transitioning from employer health insurance, signing up for Part B is more than just clicking a button online. You’ll likely need:
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- CMS-40B: Application for Enrollment in Medicare Part B
- CMS-L564: Request for Employment Information, completed and signed by your (or your spouse’s) employer
- CMS-40B: Application for Enrollment in Medicare Part B
Many people mistakenly think their employer automatically handles the CMS-L564, but they don’t. You’ll need to print the form, fill out your section, and have your HR department complete theirs.
Some retirees report successfully submitting the Medicare application online, only to realize later they needed to send in the CMS-L564 separately to prove they had creditable coverage. It’s crucial to coordinate the timing and ensure Social Security receives all forms together.
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- You can apply online at ssa.gov/medicare.
- Alternatively, call 1-800-772-1213 or visit your local SSA office.
- You can apply online at ssa.gov/medicare.
- Apply Online or In Person
The fastest way to enroll is through the Social Security website. You can also:
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- Call 1-800-772-1213
- Visit your local Social Security office (appointments recommended; some offices no longer accept walk-ins)
- Call 1-800-772-1213
If you apply online and miss uploading the CMS-L564, you may need to mail it to your local SSA office. Keep copies of all submitted documents and track your application status.
Tip: Some retirees say calling Medicare directly at 1-800-MEDICARE (1-800-633-4227) helped them retrieve their Medicare Beneficiary Identifier (MBI) if they misplaced their card.
5. Wait for Confirmation
Once enrolled, you’ll receive a Medicare card showing your Part A and Part B start dates.
How Much Will Medicare Part B Cost?
The standard monthly premium for Part B in 2025 is $185. However, high-income earners may pay more due to the Income-Related Monthly Adjustment Amount (IRMAA).
| Annual Income (Individual) | Annual Income (Joint) | 2025 Monthly Premium |
| $106,000 or less | $212,000 or less | $185.00 |
| $106,001 – $133,000 | $212,001 – $266,000 | $259.00 |
| $133,001 – $167,000 | $266,001 – $334,000 | $370.00 |
| $167,001 – $200,000 | $334,001 – $400,000 | $480.90 |
| $200,001 – $500,000 | $400,001 – $750,000 | $591.90 |
| $500,000 and above | $750,000 and above | $628.90 |
You can appeal an IRMAA surcharge if your income has dropped due to retirement or other life events.
Common Pitfalls to Avoid
- Assuming Retiree Coverage Protects You: Retiree health insurance and COBRA don’t count as creditable coverage for delaying Part B without penalty.
- Forgetting CMS-L564: Social Security requires proof of prior employer coverage to approve SEP enrollment without late penalties.
- Delaying Part D: After your employer drug coverage ends, you have only 63 days to enroll in a Part D plan to avoid penalties.
It’s not uncommon for retirees to believe they can delay enrollment because their company insurance continues after retirement. Medicare rules are clear: only active employment coverage allows you to defer Part B penalty-free.
Some retirees report their Part B applications were processed in as little as one week online, while others say it took 60 days—especially when mailing forms. Visiting a Social Security office in person can often speed things up dramatically.
Should You Enroll at 65 or Delay?
If you’re still working and covered by an employer plan with 20 or more employees, you can delay enrolling in Part B. But if your employer has fewer than 20 employees, Medicare typically becomes your primary insurer at 65, and delaying Part B could leave you without coverage.
Timeline: How Quickly Does Coverage Start?
Once your application is processed, Part B coverage typically starts the first day of the month after enrollment is approved. However, enrollment processing times can vary:
- Online applications: 1–4 weeks
- Paper forms mailed in: Up to 60 days
- In-person SSA visits: Same day in some cases
Next Steps
Watch this video for a quick overview on enrolling in Medicare Part B.
Here is the link to the Social Security website for enrollment and questions.
As Medicare Insurance Broker, another question I receive is:
How much will I have to pay for Part B? Great question! Here is Medicare’s the information on Medicare Premiums: Rules for Higher-Income Beneficiaries.
Remember for some folks, starting Medicare at age 65 is going to be a fantastic choice. For others, they might benefit from waiting a few years and staying on the company plan.
If you’re not sure, you can review this video on “When should I start Medicare”
Email your questions to Karl@TheBig65.com or just book a time on my calendar and we can chat.
Let me know how we can help!
Karl Bruns-Kyler is a licensed sales agent with no affiliation to Medicare, CMS or any governmental organization.
The Big 65 Medicare Insurance Services does not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all your options.