Medicare Part B Late Enrollment Penalty: What It Costs and How to Avoid It

If you didn't sign up for Medicare Part B when you were first eligible and don't qualify for an exception, Medicare adds a permanent surcharge to your monthly premium. It's called the Part B late enrollment penalty, and it never goes away.

How the Penalty Is Calculated

The math is straightforward:

1. Count the number of full 12-month periods between the end of your Initial Enrollment Period and your actual enrollment date
2. Multiply that number by 10%
3. Apply that percentage to the current standard Part B premium

The standard Part B premium for 2026 is $202.90/month. Here's what the penalty looks like at different delay periods:

Someone who delayed Part B by just 2 years pays an extra $486.96 every year — and that amount grows as the base premium increases. Over 20 years of Medicare, a 20% penalty adds up to nearly $10,000 in extra costs.

When the Penalty Applies

You face the Part B late enrollment penalty if all three of these are true:

• You didn't enroll in Part B during your Initial Enrollment Period (the 7-month window around your 65th birthday)
• You didn't have qualifying coverage that lets you delay without penalty (more on this below)
• You weren't enrolled in Part B for one or more full 12-month periods when you could have been

Your Initial Enrollment Period (IEP)

Your IEP is a 7-month window:

• Starts 3 months before the month you turn 65
• Includes your birthday month
• Ends 3 months after your birthday month

If you enroll in the first 3 months, coverage starts the 1st of your birthday month. If you enroll later in the window, coverage is delayed by 1–3 months. Either way, enrolling during the IEP avoids the penalty entirely.

The General Enrollment Period: Your Backup Option

If you missed your IEP, you can enroll during the General Enrollment Period (GEP):

• When: January 1 – March 31 each year
• Coverage starts: July 1 of that year
• Penalty: Yes — you will pay the late enrollment penalty permanently

That's potentially a gap of months without Part B coverage, plus the permanent penalty on top. It's a costly combination.

Exceptions: When You Can Delay Without Penalty

There is one main exception that protects you from the penalty:

Key requirements for this exception:

• Active employment — you or your spouse must be currently working (not retired)
• 20+ employees — the employer must have 20 or more employees
• Group health plan — you must be covered under the employer's plan

What Does NOT Count

• COBRA — it's post-employment coverage, not through active employment. Read why COBRA is a penalty trap →
• Retiree coverage — same problem: you're no longer actively employed. Learn about retiree coverage and Medicare →
• Individual/marketplace plans — only group employer coverage qualifies
• VA coverage — does not protect against the Part B penalty
• Employers with fewer than 20 employees — Medicare is primary in this case; you should enroll during your IEP

The 8-Month Special Enrollment Period

When your qualifying employer coverage ends (or your employment ends, whichever comes first), you have an 8-month Special Enrollment Period to enroll in Part B:

• Starts the month after employment or coverage ends (whichever is first)
• Lasts 8 months — no extensions
• No penalty if you enroll during this window
• Coverage starts the month after you enroll

Don't wait until the end of the 8 months. Enroll as soon as your employer coverage ends to avoid any gap. Read our full guide on working past 65 and Medicare →

Common Mistakes That Lead to the Penalty

1. Thinking COBRA Protects You

This is the single most common mistake. People leave a job at 64 or 65, elect COBRA, and assume they're covered. COBRA keeps your health insurance active — but it does not count as employer coverage for Medicare purposes. If you turn 65 on COBRA, you must enroll in Part B during your IEP.

2. Believing You Don't Need Part B Because You're Healthy

Part B covers doctor visits, outpatient care, preventive screenings, durable medical equipment, and more. Health status can change without warning. Skipping Part B because you feel fine now means you'll pay a permanent penalty when you eventually need it.

3. Waiting Too Long After Employer Coverage Ends

Your Special Enrollment Period is exactly 8 months. After that, you have to wait for the General Enrollment Period (Jan–Mar), coverage won't start until July, and you'll owe the penalty. Mark your calendar the day your employer coverage ends.

4. Working for a Small Employer (Under 20 Employees)

If your employer has fewer than 20 employees, Medicare is your primary insurance even while you're still working. You do not get a Special Enrollment Period based on this coverage. Enroll in Part B during your IEP.

5. Confusing Part A with Part B

Part A (hospital insurance) is premium-free for most people and can be enrolled retroactively. Part B (medical insurance) has a premium, strict enrollment windows, and the late penalty. They're separate — enrolling in Part A does not protect you from the Part B penalty.

Impact on Other Medicare Coverage

The Part B penalty doesn't just affect your Part B premium — it creates a chain reaction:

• Medigap: You need Part B to buy a Medigap policy. Your guaranteed issue rights — the period when insurers must sell you Medigap at standard rates regardless of health — are tied to your Part B effective date. Delay Part B, and you may lose access to affordable Medigap coverage. Learn about Medigap guaranteed issue rights →
• Medicare Advantage: You must have Part B to enroll in a Medicare Advantage plan. If you're waiting for the GEP and coverage doesn't start until July, you can't join an MA plan until then either.
• Coverage gap: If you need care during the months between losing other coverage and Part B starting, you're responsible for 100% of costs.

How to Avoid the Penalty

Frequently Asked Questions