Medicare Part B and Part D Late Enrollment Penalties: How They Are Calculated and Whether You Can Appeal

Medicare Part B and Part D Late Enrollment Penalties: How They Are Calculated and Whether You Can Appeal - featured image

Medicare enrollment rules can feel like a maze of deadlines, exceptions and percentages, and one missed window can follow you for life. The late enrollment penalties for Part B and Part D are among the most misunderstood parts of the system, and they catch many people out. This is especially true for those leaving work, managing a disability, or relying on a spouse’s employer coverage.

The good news is that these penalties follow clear formulas, and in many cases they can be avoided, reduced or challenged. In this guide, we’ll explore how the Part B late enrollment penalty is calculated, how the Part D late enrollment penalty works, what counts as acceptable coverage, and whether you can appeal. Our goal is to give you practical, plain-English steps rather than jargon.

Table of Contents

What Are Medicare Late Enrollment Penalties, and Why Do They Exist?

A late enrollment penalty (LEP) is a permanent surcharge added to your monthly Medicare premium if you delay signing up for certain parts of Medicare without qualifying coverage in the meantime. The principle is the same as in other insurance: coverage works best when healthy people join early, so Medicare discourages waiting until you are sick.

Two parts of Medicare carry these penalties:

Part B (medical insurance): covers doctor visits, outpatient care, preventive services and durable medical equipment.
Part D (prescription drug coverage): covers medications through private plans approved by Medicare.

Part A usually has no penalty if you or your spouse paid Medicare taxes for at least 40 quarters, because it is premium-free for most people. If you must buy Part A, a late penalty of 10% does apply. Our explainer on Medicare Parts A, B, C and D: what each part covers and costs gives a fuller picture of how the parts fit together.

Quick Comparison: Part B vs Part D Late Enrollment Penalty

Before the detail, here is a side-by-side view of how the two penalties differ.

Feature	Part B Penalty	Part D Penalty
Trigger	Not enrolling when first eligible and no qualifying employer coverage	Going 63+ consecutive days without Part D or creditable drug coverage
Formula	10% of the standard premium for each full 12-month period of delay	1% of the national base beneficiary premium for each full uncovered month
Does it change over time?	Percentage stays fixed, but the dollar amount rises with the standard premium	Percentage stays fixed, but the dollar amount changes as the national base premium changes
How long does it last?	As long as you have Part B	As long as you have Part D
Who sets it?	Social Security / CMS	Your Part D plan, based on CMS data
Formal appeal route?	Limited; mostly requests for reconsideration or equitable relief	Yes, reconsideration by an independent reviewer

How the Medicare Part B Late Enrollment Penalty Is Calculated

The Part B penalty is simple in structure, though it can be costly. For every full 12-month period you could have had Part B but did not, your premium rises by 10%. It is added for as long as you remain enrolled.

The Rules That Matter

Only full 12-month periods count. If you are late by 23 months, you are charged for one period (10%), not two.
The penalty is applied to the current standard premium, not the premium from when you were first eligible.
It is permanent. It does not expire after a number of years.
It is charged on top of any income-related adjustment (IRMAA) if your income is high enough.

A Worked Example

The standard Part B premium was $185.00 per month in 2025, with a deductible of $257. Figures are updated each year, so always check the current amounts on Medicare.gov.

Suppose you turn 65 and your Initial Enrollment Period ends, but you do not sign up until 3 years and 8 months later, with no qualifying employer coverage during that time.

Full 12-month periods of delay: 3
Penalty percentage: 3 × 10% = 30%
Monthly penalty: 30% × $185.00 = $55.50
Total monthly premium: $185.00 + $55.50 = $240.50
Extra cost per year: $666.00

Because the penalty rises each time the standard premium rises, the dollar amount keeps growing across your retirement. Over 20 years, even a modest penalty can cost many thousands of dollars.

Key Part B Dates and How They Interact With Penalties

Timing is everything. Your Initial Enrollment Period (IEP) is a seven-month window: the three months before the month you turn 65, your birthday month, and the three months after. For a full walk-through of these deadlines, see Medicare Initial Enrollment Period: key dates, deadlines and how to avoid late penalties.

If you miss that window, you can still sign up during the General Enrollment Period (January 1 to March 31). Coverage then begins the month after you enroll, but the penalty will apply unless an exception covers you. For a broader look at how enrollment windows work across insurance types, our guide to insurance enrollment periods and key enrollment dates is a helpful companion.

When You Can Delay Part B Without a Penalty

This is where many people breathe a sigh of relief. You will not owe a Part B penalty if you delayed because you had creditable coverage based on current employment and enrolled on time once it ended.

The Special Enrollment Period for Working Seniors

If you or your spouse are still working and covered by an employer’s group health plan, you can generally delay Part B without penalty. You then get an 8-month Special Enrollment Period that begins the month after employment ends or the group coverage ends, whichever comes first.

Important conditions to check:

Employer size matters. For Medicare to be secondary to employer coverage (the arrangement that makes delay safe), the employer typically needs 20 or more employees. Smaller employers often require you to take Part B, because Medicare pays first.
The coverage must be based on current employment. Coverage from active work counts.
COBRA does not count. Nor does retiree coverage, nor Marketplace coverage. Relying on these is one of the most common causes of surprise penalties.

We cover this decision in more detail in turning 65 while still working: choosing between employer coverage and Medicare.

A Note for Those on Disability

If you receive Social Security Disability Insurance (SSDI), you are usually enrolled automatically in Parts A and B after 24 months of benefits. Because Part B is automatic, the penalty risk is lower, though it can arise if you decline Part B and later reverse that decision without qualifying coverage.

Income replacement matters here. Your Part B premium is typically deducted directly from your Social Security benefit, so a penalty reduces your monthly net income. If you also receive private long-term disability payments, check how your policy treats other income, as some plans reduce benefits when Social Security or Medicare-related income changes. Planning ahead helps you avoid a shortfall in the income you rely on.

How the Medicare Part D Late Enrollment Penalty Is Calculated

The Part D penalty works differently from Part B, and it is based on uncovered months rather than years. It applies if, after your Initial Enrollment Period ends, you go 63 days or more in a row without Part D or other creditable prescription drug coverage.

The Formula in Plain English

The penalty is calculated like this:

Count the full, uncovered months you went without creditable drug coverage.
Multiply that number by 1%.
Multiply the result by the national base beneficiary premium for the current year.
Round to the nearest $0.10.
Add the result to your monthly Part D plan premium.

The national base beneficiary premium was $36.78 in 2025. It is reset each year, which means your penalty amount can change even though your uncovered months stay the same.

Worked Examples

Example 1: A 20-month gap

Uncovered months: 20
Penalty percentage: 20%
20% × $36.78 = $7.356, rounded to $7.40 per month
Annual cost: about $88.80

Example 2: A 40-month gap

Uncovered months: 40
Penalty percentage: 40%
40% × $36.78 = $14.712, rounded to $14.70 per month
Annual cost: about $176.40

These amounts may look small beside the Part B penalty, but they are lifelong and they apply on top of whichever plan premium you choose. Switching plans does not remove the penalty. It follows you to every Part D plan.

What Counts as “Creditable” Drug Coverage?

Coverage is creditable if it is expected to pay, on average, at least as much as Medicare’s standard drug coverage. Common sources include:

Employer or union plans (your plan should send a creditable coverage notice each year)
TRICARE
VA benefits
Federal Employees Health Benefits (FEHB) plans
Some Indian Health Service coverage

Always keep the annual notice from your employer or plan. It is the main evidence you will need if the penalty is ever disputed.

Extra Help Can Remove the Penalty

If you qualify for Extra Help, also known as the Low-Income Subsidy, you do not pay the Part D late enrollment penalty. For a clear explanation of how this program works alongside plan choice, see our guide to the best insurance for seniors to cover prescription drug costs, including Part D and Extra Help programs.

Common Myths vs Facts About Medicare Late Enrollment Penalties

Misunderstandings cause more penalties than genuine neglect. Here are the most common ones, set against the facts.

Myth	Fact
“The penalty goes away after a few years.”	Both penalties are generally permanent while you have the coverage.
“COBRA or retiree coverage lets me delay Part B safely.”	They do not qualify as current-employment coverage for Part B purposes.
“I don’t take medications, so I don’t need Part D.”	Without creditable coverage, the penalty clock still runs after your IEP ends.
“Changing my Part D plan resets the penalty.”	The penalty follows you to any new plan.
“The Part B penalty is based on my original premium.”	It is based on the current standard premium, so it grows over time.
“Marketplace coverage counts as creditable employer coverage.”	It does not protect you from the Part B penalty.

Can You Appeal a Part B Late Enrollment Penalty?

Appealing a Part B penalty is harder than appealing a Part D penalty, because the process is not as structured. Even so, there are routes worth knowing about.

Request a Reconsideration

If you believe the penalty was calculated incorrectly, for example because Social Security did not count months you had employer coverage, you can ask for reconsideration. You will need to show proof, such as:

Employer verification that you were covered through active employment
Dates of employment and coverage
Form CMS-L564 (Request for Employment Information), completed by your employer, which is used to verify group coverage

Seek Equitable Relief

In limited circumstances, CMS may grant equitable relief if your delay resulted from misinformation or an error by the federal government. Examples include being told incorrectly by Social Security, CMS or 1-800-MEDICARE that you did not need Part B. This can lead to a Special Enrollment Period or penalty removal.

Relief is not automatic. Your case is stronger if you have documentation, such as notes of the call (date, time, name of the representative) or written correspondence.

Check for State Assistance

Some people qualify for a Medicare Savings Program run by their state, which may help pay Part B premiums. Eligibility depends on income and resources, and rules vary by state, so contact your State Medicaid office. For related guidance, see Medicaid vs Marketplace coverage: income limits, eligibility and how to switch between them.

Can You Appeal a Part D Late Enrollment Penalty?

Yes, and the process is more formal. A Part D penalty can be challenged through a reconsideration handled by an independent review entity, which is separate from your plan.

Step-by-Step: How the Part D Penalty Reconsideration Works

Review your notice. Your plan will send a letter explaining the penalty and the number of uncovered months it counted.
Check the facts. Compare the months counted against your own records of creditable coverage.
Complete the reconsideration request form included with your notice.
Submit it within 60 days of the date on the notice (check your letter for the exact deadline and extensions).
Attach evidence where possible, such as creditable coverage notices, employer letters or benefits statements.
Wait for the decision. The independent reviewer will issue a written decision.
Escalate if needed. If you disagree, further levels of appeal, including an administrative law judge, may be available depending on the amount in dispute.

Common Grounds That Succeed

Appeals most often succeed when one of the following applies:

You had creditable coverage that your plan did not know about
You were not told your coverage was non-creditable when you should have been
You qualified for Extra Help during some of the period
The plan counted months incorrectly
You were affected by a qualifying exceptional circumstance (for example, a natural disaster or misinformation)

Tips for Building a Strong Appeal

Act quickly. Deadlines are firm.
Be specific. State the exact months in dispute and why.
Keep copies of everything you send.
Use clear, polite language, which helps reviewers focus on the facts.

For general guidance on structuring any insurance dispute, including timelines and what to include, our guide to filing an effective insurance appeal with a sample dispute letter, timeline expectations and cost considerations provides a useful framework. If your dispute concerns a denied claim rather than a penalty, our walkthrough on how to appeal a denied health insurance claim, covering internal appeals, external review and Medicare levels is the better fit.

Part B vs Part D: Appeal Options at a Glance

Issue	Part B	Part D
Who handles disputes?	Social Security / CMS	Plan, then independent review entity
Formal deadline?	Varies; act promptly after the notice	Generally 60 days from the notice date
Best evidence	Employer coverage verification, written misinformation	Creditable coverage notices, benefit statements
**Typical successful reasons