Joining Medicare After 65: What You Should Know

Q: Do I need to sign up for Medicare Part A if I'm still working?

Most people enroll in Part A at 65 because it is premium-free. However, if you contribute to an HSA, you must delay Part A, as Medicare enrollment makes you ineligible for HSA contributions.

Q: What happens if my employer has fewer than 20 employees?

At companies with fewer than 20 employees, Medicare becomes the primary payer at age 65. You must enroll in Part B during your Initial Enrollment Period to avoid unpaid medical bills.

Q: How does IRMAA affect late enrollees?

IRMAA surcharges are based on income from two years prior. Late enrollees whose income has dropped significantly upon retirement can appeal these surcharges using Form SSA-44.

Key Takeaways:

Employer Size: Confirm your company has 20 or more employees to avoid mandatory Part B enrollment.
HSA Restriction: End all Health Savings Account contributions before starting any part of Medicare to avoid penalties.
Special Enrollment: Sign up for Medicare within eight months of leaving your job to bypass late surcharges.

For most people, the 65th birthday marks an automatic entry into the Medicare system. However, for high-earning professionals and executives, this milestone is often just another workday. If you are part of the growing number of Americans working well into your late sixties, Medicare enrollment is not a simple “yes or no” choice. Instead, it is a strategic financial decision that requires precision.

Delaying enrollment can be a brilliant move to save on premiums, but only if you follow the federal guidelines perfectly. One minor clerical error or a misunderstanding of your current employer coverage can trigger lifelong financial consequences. This guide provides the roadmap you need to join Medicare on your own terms while protecting your retirement assets.

The Core Rule: Creditable Coverage vs. The Penalty

The most common fear among late enrollees is the Part B late enrollment penalty. This penalty adds a permanent 10% surcharge to your monthly premium for every year you were eligible but didn’t sign up. To avoid this, you must prove you have “creditable coverage.”

Creditable coverage is insurance that Medicare considers at least as good as its own. For the 63–70 audience, the most important factor is the size of the employer providing that coverage. If you or your spouse are still working, you can explore the specific requirements for delaying Medicare without penalties to ensure your current plan meets the federal standard.

What is Creditable Coverage?

Medicare typically recognizes employer group health plans as creditable only if the company has 20 or more employees. If your firm is smaller than this, Medicare usually becomes the “primary” payer at age 65. In that scenario, failing to enroll in Part B could leave you with massive unpaid medical bills, as your small-group insurance may refuse to pay until Medicare pays its share first.

The High Cost of Inaction: Permanent Part B Penalties

If you miss your enrollment window without having creditable coverage, the costs are steep. The 10% penalty is not a one-time fee; it stays with you for life. Furthermore, you may only be allowed to sign up during the General Enrollment Period, which could leave you without any outpatient coverage for months. Protecting your wealth means verifying your “creditable” status with your HR department every single year.

Working Past 65: When to Enroll and When to Wait

If you work for a large employer (20+ employees), you generally have the option to delay Medicare Part B and Part D. This allows you to stay on your high-quality employer plan and avoid the monthly Part B premium. However, many professionals choose to enroll in Medicare Part A even while working. Part A covers hospital stays and is usually premium-free if you have worked for 10 years or more.

There are nuances to this strategy if you contribute to a Health Savings Account (HSA). Once you enroll in any part of Medicare, you can no longer contribute to an HSA. Navigating these Medicare rules working past 65 is essential to avoid tax penalties and maximize your healthcare savings during your final working years.

Navigating Coverage While You or a Spouse Are Employed

Many of our clients are covered by a spouse’s employer plan rather than their own. The same rules apply: as long as the spouse is “actively” working and the company is large enough, you can typically delay enrollment. However, you must ensure the employer plan covers prescription drugs at a creditable level to avoid Part D penalties later.

The Hidden Trap: COBRA and Retiree Health Plans

This is perhaps the most dangerous area for those over 65. If you retire and take COBRA or a retiree health plan, Medicare does not consider this “active employment” coverage. Many people mistakenly believe they can wait until COBRA ends to sign up for Medicare. This is incorrect. If you are 65 or older and on COBRA, you must enroll in Medicare Part B immediately to avoid penalties and coverage gaps.

The Special Enrollment Period (SEP) for Late Enrollees

Once you decide to stop working or you lose your employer coverage, a new clock begins to tick. This is known as the Special Enrollment Period (SEP). This window allows you to sign up for Medicare without any late penalties, regardless of how many years have passed since you turned 65.

Managing this timeline to apply for Medicare is the key to a stress-free transition. Missing this window by even a few days can lock you out of coverage until the following year.

Your 8-Month Window: The Timeline After Employment Ends

The SEP lasts for eight months, beginning the month after your employment ends or your group health coverage ends—whichever happens first. While eight months sounds like a long time, you should ideally start the process three months before you retire. This ensures your Medicare coverage starts the very first day you are no longer covered by your employer.

Avoiding Coverage Gaps: Coordinating COBRA and Medicare

If you are offered COBRA at retirement, you can take it, but it should usually be secondary to Medicare. Medicare will be your primary insurance. COBRA will only pay for costs that Medicare doesn’t cover. Because COBRA is often expensive, most retirees find that pairing Medicare with a Medigap (Supplement) plan provides better coverage for a lower total cost.

Financial Strategy for High-Income Retirees

For our high-income clients, the cost of Medicare is not just the base premium. You must also account for the Income-Related Monthly Adjustment Amount (IRMAA). This is a surcharge added to your Part B and Part D premiums based on the income you reported on your tax returns from two years ago.

Strategic planning can help mitigate these costs. For example, in 2026, the Part D out-of-pocket spending limit has been indexed to $2,100. This provides a clear ceiling for your drug costs, but your IRMAA surcharges will still apply. Understanding how your final year of salary impacts your initial years of Medicare premiums is a vital part of your retirement cash flow analysis.

Executing Your Enrollment: Step-by-Step

When you are ready to make the jump, the process is more manual than it is for those joining at 65. You cannot simply use the standard online application in many cases. You must provide proof that you had employer coverage since you turned 65.

Learning exactly how to enroll in Medicare past 65 requires gathering specific forms from your employer. You can find more details on this process at SSA.gov.

Coordination with Social Security

The Social Security Administration (SSA) processes all Medicare enrollments. If you are already collecting Social Security benefits, you will be automatically enrolled in Parts A and B. If you are working and not yet collecting benefits, you must proactively apply through the SSA portal or by visiting a local office.

Necessary Documentation: Form CMS-L564

To prove your creditable coverage, your employer must fill out Form CMS-L564. This form verifies that you were covered by a group health plan based on “current employment.” You will submit this alongside your Part B application (Form CMS-40B). Without this documentation, the SSA will assume you had a gap in coverage and may assess a penalty.

Managing Your Bills

Once you are enrolled, you must decide how to handle your monthly premiums. If you are receiving Social Security, the premiums are deducted automatically. If you have delayed your Social Security benefits to maximize your payout, you will receive a bill every three months. Mastering how to pay Medicare bills through systems like Medicare Easy Pay can prevent accidental coverage terminations due to missed payments.

Frequently Asked Questions

Do I need to sign up for Medicare Part A if I’m still working? Most people should sign up for Part A at 65 because it is usually premium-free. However, if you contribute to a Health Savings Account (HSA), you should delay Part A. Enrolling in any part of Medicare makes you ineligible to contribute to an HSA.

What happens if my employer has fewer than 20 employees? If your employer has fewer than 20 employees, Medicare is considered your primary insurance at age 65. You must enroll in Part B during your Initial Enrollment Period to ensure your medical bills are covered. Your small-group plan will likely only pay for costs that Medicare doesn’t cover.

Does COBRA count as “active employment” coverage? No. COBRA is not considered creditable coverage based on current employment. If you are 65 or older, you must enroll in Medicare Part B within 8 months of leaving your job, even if you are on COBRA, to avoid lifelong late enrollment penalties.

How does IRMAA affect late enrollees? IRMAA surcharges apply to late enrollees just as they do to everyone else. The SSA will look at your tax returns from two years prior to determine your surcharge. If your income has dropped due to retirement, you can appeal this surcharge using Form SSA-44.

Conclusion

Joining Medicare after age 65 is a privilege afforded to those who have continued to contribute to the workforce. By understanding the rules of creditable coverage and the power of the Special Enrollment Period, you can avoid the “penalty traps” that catch many retirees. The goal is to move from your employer plan to Medicare without a single day of overlapping costs or missing coverage. With a proactive approach and a clear understanding of the 2026 regulations, your transition to Medicare can be as successful as your career.

Working Past 65? Your Step-by-Step Roadmap to Navigating Medicare Enrollment