COBRA and Medicare Part B Penalty: How to Avoid It

Introduction

You leave your job at 64 or 65 and COBRA arrives in the mail. It looks like employer coverage, so delaying Medicare Part B seems safe. It often isn't.

COBRA does not count as coverage based on current employment for the Part B Special Enrollment Period. Miss the window and you face a lifelong premium surcharge and a gap in coverage.

The Part B penalty is 10% for each full 12-month period you could have had Part B but didn't sign up.

This guide covers how active employer coverage differs from COBRA, when Medicare should start, how Parts A, B, and D interact with COBRA, and what to do before you decide.

Key Takeaways

• COBRA does not let you delay Part B without penalty.
• The 8-month clock starts when employment or active coverage ends, not when COBRA ends.
• Part D creditable coverage follows separate rules from Part B.
• Confirm dates with Social Security before declining Part B.

Medicare Part B and COBRA: The Rule That Matters

Why Part B timing matters

Part B covers medically necessary and preventive services, including ambulance services, durable medical equipment, mental health services, and limited outpatient drugs.

Medicare.gov's official penalty example shows that a 24-month delay without a qualifying Special Enrollment Period (SEP) produces a 20% penalty, or about $243.50/month in 2026. The standard 2026 premium is $202.90 with a $283 deductible. The penalty generally lasts as long as you have Medicare.

COBRA versus current employment coverage

COBRA is temporary continuation of an employer plan after a qualifying event, such as job loss or reduced hours. You pay the full cost, up to 102%. Active coverage through your own or a spouse's current job is different. Only that kind of coverage supports a penalty-free Part B delay.

The 8-month window

The working-coverage SEP lets you enroll while current-employment coverage continues, or within 8 months after the employment or that coverage ends, whichever comes first. Medicare.gov states that COBRA does not count for this purpose or restart the clock.

If you miss the working-coverage SEP, two other enrollment windows still matter:

• Your Initial Enrollment Period is 7 months: 3 before your birthday month, the month itself, and 3 after.
• The General Enrollment Period (January 1 to March 31) is the fallback, and penalties may apply.

Warning: Employers, COBRA administrators, and insurers don't decide your Medicare obligations. "You have employer coverage" is not an answer. Confirm with Medicare or Social Security.

How Medicare and COBRA Coordinate

Medicare first, COBRA second

For age-based Medicare, Medicare pays first and COBRA is secondary. If you're eligible for Medicare but haven't enrolled, COBRA may pay only a small portion, leaving you with most of the bill.

Medicare entitlement and COBRA termination

Timing relative to your COBRA election matters:

• Medicare entitlement before or on your COBRA election date cannot be the reason COBRA ends.
• If you first become entitled after electing COBRA, the plan may end your COBRA on the entitlement date.
• Entitlement means effective enrollment in Part A or B, whichever is earlier. Eligibility alone isn't entitlement.

The Department of Labor states that adding Part B while on COBRA does not affect that COBRA coverage.

A simple timeline

1. Employment ends and group health coverage stops.
2. COBRA begins (typically the day after coverage ends).
3. You reach Medicare eligibility age or qualify on another basis.
4. You complete Part B enrollment before the 8-month Special Enrollment Period closes.
5. COBRA continues or ends, depending on plan terms and when Medicare entitlement took effect.

Spouses and dependents

Ending one person's COBRA doesn't automatically end other qualified beneficiaries' rights. If employee Medicare entitlement came less than 18 months before job loss, dependents may get up to 36 months from the entitlement date.

In DOL's example, entitlement 8 months before termination leaves dependents up to 28 months after termination. Ask the plan administrator for answers that apply to each dependent.

How to Avoid the Medicare Part B Penalty: A Practical Timeline

1. Identify your coverage source before you turn 65: your job, a spouse's job, retiree coverage, COBRA, Marketplace, VA, or another plan. Only current-employment coverage supports a delay. Employer size also matters for who pays first: with 20 or more employees the group plan generally pays first; with fewer, Medicare does.

2. Record the key dates: Initial Enrollment Period, last day of work, last day of active coverage, COBRA election date, and expected COBRA end date.

3. Get written confirmation from your employer or benefits administrator that coverage is based on current employment, and whether the drug plan is creditable for Part D. Complete form CMS-L564 so the employer section documents employment and group coverage dates.

4. Contact Social Security or Medicare before declining Part B. Use CMS-40B or SSA's online working-SEP process, and keep proof of submission and effective dates. If your employer can't sign, SSA accepts alternatives such as W-2s, premium pay stubs, or dated insurance cards.

5. Coordinate Parts A, B, and D. One decision doesn't govern all three. Part D creditable-coverage rules differ from Part B rules.

6. Write a transition plan showing who pays first, when COBRA starts or ends, when Medicare takes effect, and what drug and supplemental coverage follows.

You can ask for a Part B start date up to 3 months later if you enroll while working or in the first full month after employer coverage ends. Use the remarks field on the application.

Costs, Part D, and Supplemental Coverage

What to compare

• COBRA premiums: up to 102% of total plan cost, plus administrative charges (150% during a disability extension)
• Part B: $202.90/month in 2026, higher with income
• Part D, Medigap, and Medicare Advantage premiums (vary by plan and location)

Income-related adjustments apply based on 2024 income. CMS's 2026 fact sheet puts Part B at $284.10 for individuals above $109,000 and up to $649.20 or $689.90 at the top brackets.

Part D and creditable coverage

Creditable coverage is drug coverage expected to pay, on average, as much as standard Medicare drug coverage. COBRA drug coverage isn't automatically creditable. Request the creditable coverage notice from your employer (required annually before October 15 and on request) and keep a copy.

The Part D penalty can apply after 63+ consecutive days without Part D or creditable coverage. It is 1% of the national base premium ($38.99 in 2026) per uncovered month. When employer or COBRA coverage ends, you get a Part D SEP of 2 full months after the month it ends.

Medigap, Medicare Advantage, and help with costs

• Medigap supplements Original Medicare. Medicare Advantage replaces how you receive Parts A and B through a private plan.
• Medigap Open Enrollment lasts 6 months from when you have Part B and are 65+. Insurers can't use medical underwriting then.
• Medicare Savings Programs (QMB, SLMB, QI, QDWI) may help with premiums and cost-sharing.

Weigh total premiums and out-of-pocket costs against your doctors, prescriptions, and budget before you leave COBRA or enroll in Part B.

If You Delayed Part B or Are Turning 65 While on COBRA

Immediate actions

• Call Social Security and Medicare.
• Ask your COBRA administrator for written coverage and termination details.
• Gather employment and coverage records.
• Find out which enrollment period is open to you now.

If you missed the window

Ask about current enrollment options, effective dates, and penalty consequences. Possible routes include:

• Misinformation SEP, if qualifying employer or plan misinformation on or after January 1, 2023 caused you to miss enrollment
• Exceptional-conditions SEP using form CMS-10797
• Equitable relief for government error; hardship alone does not qualify
• Reconsideration with SSA, generally within 60 days

None is an automatic waiver.

Getting help

Muneris Benefits' licensed agents, including Lauren Hand and Baylee Davis, provide Medicare guidance and help compare Medicare Advantage, Medicare Supplement, and prescription drug options. Official enrollment determinations come from Medicare and Social Security.

Frequently Asked Questions

Does Medicare recognize COBRA as creditable coverage?

Only for drugs, and only if the plan's drug coverage is creditable, which protects Part D timing. It doesn't give you a Part B SEP. Verify your situation with Medicare or Social Security.

Do you need COBRA if you have Medicare?

Generally not. Each beneficiary elects independently. COBRA may pay secondary benefits, so weigh its cost, plan rules, and your needs.

What happens if I turn 65 while on COBRA?

Review Medicare enrollment right away and confirm how COBRA coordinates or ends. Don't assume COBRA lets you delay Part B without consequence.

How much will COBRA cost per month?

It depends on the former employer's plan, covered dependents, and allowed administrative charges. Your COBRA election notice shows the exact premium.

What is the best secondary insurance if you have Medicare?

It depends on provider access, drug coverage, costs, medical needs, and eligibility. Options include COBRA, Medigap, Medicare Advantage, and retiree coverage.