Medicare · Enrollment
When Do I Have to Enroll in Medicare to Avoid a Penalty?
The Short Answer
Most people must enroll in Medicare during a 7-month Initial Enrollment Period that spans the three months before your 65th birthday, your birthday month, and the three months after. Miss it without qualifying employer coverage and you face a permanent late penalty: 10% added to your Part B premium for every full year you could have been enrolled but were not.
Medicare's deadlines are unforgiving, and the penalties are permanent, not one-time. The rules are also genuinely confusing because they interact with whether you are still working. Here is exactly when you must enroll, the one situation that lets you delay safely, and what the penalty actually costs.
What is the Medicare Initial Enrollment Period?
Your Initial Enrollment Period (IEP) is a 7-month window centered on the month you turn 65. It includes the three months before your birthday month, the birthday month itself, and the three months after.1
Enrolling in the first three months gives you the cleanest coverage start date, with benefits beginning the month you turn 65. This is the simplest, lowest-risk path for anyone who is not covered by a qualifying employer plan.
What is the late enrollment penalty?
If you miss your enrollment window without qualifying coverage, Medicare adds 10% to your Part B premium for each full 12-month period you could have had Part B but did not.2 This penalty is permanent: it is added to your premium for as long as you have Part B.
With the 2026 standard Part B premium at $202.90 per month, a two-year delay adds a 20% penalty, raising the premium to about $243 per month for life.3 There is also a separate, permanent Part D late penalty for going without prescription drug coverage.
Free Tool
Estimate your Medicare late enrollment penalty
When can I delay Medicare without a penalty?
There is one main exception. If you (or your spouse) are still working at 65 and covered by a group health plan through an employer with 20 or more employees, you can delay Part B without penalty while that coverage is active.2
When that employer coverage ends, you get an 8-month Special Enrollment Period to sign up for Part B penalty-free. Crucially, this window starts when the coverage ends, not when you retire, and COBRA and retiree coverage do NOT count as qualifying coverage for this purpose.
The trap to avoid
Employer plans with fewer than 20 employees generally do not let you delay Medicare safely, and COBRA never does. Before deciding to delay, confirm in writing with your benefits administrator that your plan qualifies. One phone call can prevent a lifetime penalty.
Frequently asked questions
How long is the Medicare late enrollment penalty?
The Part B penalty is permanent. It adds 10% to your premium for every full year you delayed, and it stays on your premium for as long as you have Part B coverage.
Does COBRA count as qualifying coverage to delay Medicare?
No. COBRA and retiree health coverage do not count as active employer coverage for Medicare purposes. Relying on COBRA to delay Part B can trigger a permanent penalty.
What is the Special Enrollment Period?
If you delayed Medicare because of qualifying employer coverage, you get an 8-month Special Enrollment Period to sign up after that coverage ends. It begins the day the employer coverage ends, not the day you retire.
Keep reading
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Medicare Late Enrollment Penalty Calculator
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Sources
- Get Started With Medicare: When to Sign Up Medicare.gov. Initial Enrollment Period structure and coverage start dates.
- Avoid Late Enrollment Penalties Medicare.gov. Part B and Part D late enrollment penalties and the employer-coverage exception.
- 2026 Medicare Parts A & B Premiums and Deductibles Centers for Medicare & Medicaid Services. 2026 standard Part B premium of $202.90.