Key Takeaways

• Missing key Medicare enrollment periods in 2025 can result in late penalties and limited healthcare coverage.

• Delaying Medicare Part B or Part D enrollment without credible coverage can have long-term financial consequences.

The Critical Importance of Proper Medicare Enrollment

When you first become eligible for Medicare, typically around age 65, the timing and accuracy of your enrollment decisions directly affect both your monthly costs and the healthcare access you’ll have for the rest of your life. Making even one error during enrollment can trigger permanent penalties or result in delayed or restricted coverage.

Whether you’re approaching age 65 now or helping a loved one transition to Medicare, understanding what to do—and what not to do—can save you from years of headaches.

Missing the Initial Enrollment Period (IEP)

The Initial Enrollment Period is a seven-month window:

• It starts three months before your 65th birthday month

• Includes your birthday month

• Ends three months after your birthday month

Failing to enroll in Medicare during this time, if you’re not covered by credible group health insurance through your or your spouse’s active employment, can result in late enrollment penalties for Medicare Part B and Part D. These penalties are not one-time fees—they accumulate and apply for life.

Assuming Employer Coverage Is Always Creditable

One of the most common mistakes people make is assuming that any employer coverage will exempt them from enrolling in Medicare during the IEP. In 2025, Medicare only considers employer coverage “creditable” if:

• It comes from an employer with 20 or more employees

• The plan provides benefits as good as or better than Medicare (especially for drug coverage)

If you delay Medicare Part B or Part D while covered under a non-creditable plan, you will face late penalties and may experience gaps in coverage.

Delaying Part B Without Proper Documentation

If you do have credible employer coverage and delay enrolling in Medicare Part B, make sure you get proof of credible coverage from your employer. This documentation is required when you later enroll during a Special Enrollment Period (SEP). Without it, you may be denied the SEP and forced to wait until the General Enrollment Period (January 1–March 31), with coverage not starting until July 1.

Overlooking Part D Enrollment or Choosing to Skip It

Prescription drug coverage under Medicare Part D is optional—but skipping it without other credible drug coverage leads to another lifelong penalty. The penalty equals 1% of the national base premium for each full month you were eligible but didn’t enroll.

Even if you don’t take prescriptions now, enrolling in a Part D plan during your IEP is a wise move. You can choose a lower-cost plan to maintain your eligibility and avoid future penalties.

Believing Medicare Happens Automatically

Medicare does not always enroll you automatically at age 65. You’ll only be automatically enrolled in both Parts A and B if you are already receiving Social Security or Railroad Retirement Board benefits at least four months before turning 65.

If you’re not receiving those benefits, you must actively sign up. Failing to do so during your IEP can trigger penalties and leave you without health insurance.

Enrolling in Medicare Part B When You Have an HSA

In 2025, you can’t contribute to a Health Savings Account (HSA) while enrolled in any part of Medicare. Many people don’t realize that enrolling in Medicare Part A alone disqualifies them from making HSA contributions.

If you’re still working and want to continue HSA contributions, you must delay both Part A and Part B—but only if your group health plan is creditable. Consult your HR department and a licensed agent before making this choice.

Choosing Plans Without Understanding Out-of-Pocket Costs

Many Medicare beneficiaries choose plans based on premiums alone, but that can be shortsighted. A lower premium may mean:

• Higher deductibles

• Increased coinsurance

• Limited provider networks

Understanding what you may pay out of pocket each year is crucial. This includes potential costs for hospitalization, specialist visits, emergency services, and prescription drugs. Remember, Medicare is not free, and underestimating these expenses can create financial strain in retirement.

Ignoring Medicare Enrollment Deadlines for Retirees Under FEHB

If you’re a retiree under the Federal Employees Health Benefits (FEHB) program, you may think you’re fully covered and don’t need Medicare. However, if you retire and are eligible for Medicare, you should consider enrolling in at least Part A and Part B, especially because FEHB plans coordinate differently once you’re no longer actively employed.

Not enrolling may lead to:

• Increased out-of-pocket costs under FEHB

• Delayed Medicare coverage

• Part B late enrollment penalties if you miss the SEP

Assuming Medicare Covers Everything

Another widespread mistake is assuming that once you’re on Medicare, all your healthcare needs will be covered. But in 2025, Medicare does not cover:

• Most dental, vision, and hearing services

• Long-term custodial care

• Routine foot care

• Cosmetic procedures

You may need to explore separate supplemental insurance or set aside funds for these costs.

Confusing Enrollment Periods and Making the Wrong Change

Beyond the IEP, there are other enrollment windows you must understand:

• General Enrollment Period (GEP): January 1 to March 31 if you missed IEP/SEP

• Annual Enrollment Period (AEP): October 15 to December 7 to change your Medicare health or drug plan

• Medicare Advantage Open Enrollment: January 1 to March 31, for switching Medicare Advantage plans or returning to Original Medicare

Selecting the wrong period for your intended change may cause delays or result in coverage that doesn’t begin when you expect it to.

Relying Only on Online Tools Without Human Guidance

While online resources provide general Medicare information, the system remains complex—especially when factoring in:

• Income-Related Monthly Adjustment Amounts (IRMAA)

• Employer group coverage coordination

• Travel needs

Speaking with a licensed agent listed on this website can help you:

• Review your current situation

• Identify the right enrollment period

• Avoid penalties

• Understand coordination with other coverage

Forgetting to Reassess Coverage Every Year

Even after initial enrollment, failing to reassess your plan during the Annual Enrollment Period each year can lead to:

• Higher premiums

• Prescription drugs no longer being covered

• Reduced provider networks

In 2025, plans may change their formularies, coverage areas, or out-of-pocket costs. Taking time each fall to review your Annual Notice of Change and compare plans can save you significantly.

Overlooking Income-Related Part B and D Premiums

If your income is above a certain level, you may owe IRMAA surcharges on your Medicare Part B and D premiums. These are based on your modified adjusted gross income (MAGI) from two years ago—in 2025, that means your 2023 tax return.

Failing to plan for these surcharges can cause budgeting surprises. If your income has decreased since 2023 due to retirement or life changes, you may be able to appeal these adjustments using Form SSA-44.

Thinking Enrollment Mistakes Can Be Easily Fixed Later

Unfortunately, many Medicare mistakes can’t be undone. A late enrollment penalty doesn’t go away. Missed deadlines usually mean waiting until the next enrollment window. And coverage gaps can’t be retroactively filled.

That’s why understanding your options and acting at the right time is vital. Enrolling properly isn’t just a one-time administrative task—it’s a lifelong financial and health decision.

What This Means for You in 2025 and Beyond

Medicare enrollment is a personal responsibility, and in 2025, the rules are more important than ever to follow. Whether you’re entering Medicare this year or helping someone else prepare, don’t let simple errors cost you years of higher premiums and lost benefits.

To ensure you’re making the best decisions, speak with a licensed agent listed on this website who can walk you through the specifics of your situation. Getting expert guidance now can help you avoid regret later.