Not everyone has to sign up for Medicare the month they turn 65.

That is the part that creates confusion. Some people can delay Medicare because they have active employer coverage. Other people cannot safely delay, even if they still have some kind of health insurance.

The expensive mistake is assuming all coverage protects you the same way. It does not.

If you do not sign up for Medicare at 65 and you do not have coverage that lets you delay, you can face a gap in coverage, a permanent Part B penalty, a Part D drug penalty, and a rushed plan decision later.

What Happens If You Do Not Sign Up for Medicare at 65?

If you miss your Medicare Initial Enrollment Period without qualifying coverage, three things can happen.

  1. You may have to wait for another enrollment period.
  2. Your Medicare coverage may start later than you expected.
  3. You may owe late enrollment penalties for as long as you have Medicare coverage.

The outcome depends on why you did not sign up.

If you were covered by active employer insurance from your own job or your spouse’s job, and that employer was large enough, you may qualify for a Special Enrollment Period and avoid the Part B penalty.

If you were relying on COBRA, retiree coverage, Marketplace coverage, or no coverage at all, the answer can be very different.

What Is Your Initial Enrollment Period?

Your Initial Enrollment Period is your first Medicare sign-up window around age 65. It lasts 7 months:

  1. the 3 months before your birthday month
  2. your birthday month
  3. the 3 months after your birthday month

If you enroll before your birthday month, Part B usually starts the first day of your birthday month. If your birthday is on the first day of the month, Medicare uses the month before your birthday month.

If you wait until your birthday month or one of the 3 months after, Medicare says Part B starts the next month.

That timing matters. Waiting until the end of the window may still be allowed, but it can compress your decision-making and leave less room to compare Medicare Supplement, Medicare Advantage, and Part D options.

If you want a broader planning checklist, start here: What do you need to do before turning 65?

When Can You Safely Delay Medicare at 65?

You can usually delay Medicare Part B without penalty if you have active employer coverage from your own current job or your spouse’s current job, and the employer has 20 or more employees.

The key word is active.

Coverage from a current employer is not the same as COBRA. It is not the same as retiree coverage. It is not the same as a Marketplace plan.

For Kansas City-area clients who are still working at 65, I usually start with two questions:

  1. Does the employer have 20 or more employees?
  2. Is the coverage based on current employment?

If the answer to both is yes, delaying Part B may be reasonable. If the answer to either is no, you need to slow down and verify the rules before assuming you are protected.

I explain that working-at-65 decision in more detail here: Do you need Medicare at 65 if you’re still working?

What If Your Employer Has Fewer Than 20 Employees?

If your employer has fewer than 20 employees, Medicare usually becomes primary when you turn 65.

That means your employer plan may expect Medicare to pay first. If you do not have Medicare, the employer plan may pay less than you expected or deny parts of the claim it would have coordinated with Medicare.

This is one of the most painful versions of the mistake because the person often thinks they did the responsible thing. They kept insurance. They paid premiums. They just did not realize Medicare was supposed to be primary.

If you work for a smaller employer in Missouri or Kansas, ask HR directly how the plan coordinates with Medicare at 65. Get the answer in writing if possible.

Does COBRA Let You Delay Medicare?

No. COBRA does not protect you from the Medicare Part B late enrollment penalty.

COBRA can keep you insured after employment ends, but Medicare does not treat COBRA the same way it treats active employer coverage. Your Special Enrollment Period for Part B is tied to the end of active employment or active job-based coverage, not the end of COBRA.

This is the mistake I see most often when someone retires before or around 65. They leave the job, take COBRA because it feels familiar, and assume Medicare can wait. By the time COBRA ends, their Medicare window may already be gone.

Read this before using COBRA as a bridge: Medicare and COBRA: the expensive mistake thousands of retirees make

What Is the Part B Late Enrollment Penalty?

The Medicare Part B late enrollment penalty is 10% for each full 12-month period you could have had Part B but did not sign up.

This is not a one-time fee. Medicare adds it to your monthly Part B premium, and for most people it lasts as long as they have Part B.

Medicare gives this 2026 example: if you waited 2 full years to sign up for Part B and did not qualify for a Special Enrollment Period, your penalty would be 20%. With the 2026 standard Part B premium of $202.90, that would add $40.58 per month, rounded into a $243.50 monthly premium.

That penalty may not sound huge in one month. Over 10 or 20 years, it becomes a real cost.

What About the Part D Late Enrollment Penalty?

Part D has its own penalty.

You can owe a Part D penalty if you do not join a Medicare drug plan when you first get Medicare and you go 63 days or more without creditable prescription drug coverage.

Medicare calculates the Part D penalty differently from the Part B penalty. The general rule is 1% of the national base beneficiary premium for each full month you went without Part D or other creditable drug coverage. The amount is added to your Part D premium.

This matters even if you do not take prescriptions right now. A healthy 65-year-old can skip drug coverage, feel fine for a few years, and then discover the penalty when a medication finally becomes necessary.

If your income and resources are limited, Extra Help can also affect this penalty. I covered that here: Medicare Part D Extra Help: who qualifies and how it works

What If You Have to Pay for Part A?

Most people get Medicare Part A premium-free because they or a spouse paid Medicare taxes long enough.

If you do not qualify for premium-free Part A and you have to buy it, there can also be a Part A late enrollment penalty. Medicare says the premium may go up 10%, and you may have to pay that higher premium for twice the number of years you delayed.

This does not apply to most people, but it matters for people with shorter work histories or unusual coverage situations.

What If You Already Missed Your Medicare Window?

Do not guess your way forward.

Start by figuring out whether you had coverage that qualifies you for a Special Enrollment Period. If you did, you may be able to enroll in Part B without the late enrollment penalty.

If you had active employer coverage, you may need employer documentation showing you were covered while you or your spouse were working. If you did not have qualifying coverage, you may need to use the General Enrollment Period.

The General Enrollment Period runs January 1 through March 31 each year. Medicare says coverage starts the month after you sign up. If you miss your Initial Enrollment Period and do not qualify for a Special Enrollment Period, that wait can create a gap.

After that, review your drug coverage, Medigap options, Medicare Advantage choices, and any penalty exposure before choosing a plan.

What Should You Do Before Deciding to Delay Medicare?

Before you decide not to sign up at 65, answer these questions:

  1. Am I covered through active employment or something else?
  2. Does the employer have 20 or more employees?
  3. Is my prescription coverage creditable for Part D?
  4. Am I contributing to an HSA?
  5. Am I relying on COBRA, retiree coverage, Marketplace coverage, VA coverage, or another non-employer plan?
  6. Do I have written confirmation from HR or the benefits administrator?

If any answer is unclear, get help before your Initial Enrollment Period closes.

This is also where the Medicare readiness checklist can help. It walks through employment, employer size, Social Security status, HSA issues, drug coverage, and timing in one place.

How This Comes Up in Kansas City

In the Kansas City area, this question often comes up with people who are working past 65, retiring from a local employer, moving from employer coverage to COBRA, or coordinating coverage across Missouri and Kansas.

The plan market is local, but the enrollment penalty rules are federal. That means the same mistake can affect someone in Blue Springs, Independence, Lee’s Summit, Overland Park, or anywhere else in the KC metro.

The right answer is not always “sign up immediately.” The right answer is to confirm whether you are truly allowed to delay.

If you are approaching 65 and not sure, I can review your employer coverage, timing, prescriptions, and plan options at no cost. The goal is to avoid a permanent problem before it starts.

Frequently Asked Questions

Do I have to sign up for Medicare when I turn 65?

Not always. If you have active employer coverage from your own or your spouse’s current job, and the employer has 20 or more employees, you may be able to delay Part B without penalty. If you do not have qualifying active employer coverage, delaying can create penalties and coverage gaps.

What happens if I miss my Initial Enrollment Period?

If you miss your Initial Enrollment Period and do not qualify for a Special Enrollment Period, you may have to wait for the General Enrollment Period from January 1 through March 31. Your coverage starts the month after you sign up, and you may owe late enrollment penalties.

How much is the Medicare Part B late enrollment penalty?

The Part B penalty is 10% for each full 12-month period you could have had Part B but did not sign up. For most people, the penalty is added to the monthly Part B premium for as long as they have Part B.

Does COBRA count as coverage that lets me delay Medicare?

No. COBRA does not protect you from the Part B late enrollment penalty the way active employer coverage can. Your Special Enrollment Period is tied to active employment or active job-based coverage, not the end of COBRA.

Can I delay Part D if I do not take prescriptions?

You can delay Part D only if you have other creditable prescription drug coverage or qualify for Extra Help. If you go 63 days or more without Part D or creditable drug coverage after you are eligible, you may owe a Part D late enrollment penalty later.