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The Medicare Part B SEP allows people to delay Part B enrollment if they have health coverage through their own employer or a spouse’s current employer. | Image: Dragana Gordic / stock.adobe.com

The Medicare Part B Special Enrollment Period

Planning to delay your enrollment in Part B? You can avoid a costly penalty if you meet the criteria outlined in this SEP.

Reviewed by our health policy panel.

Key takeaways

Although Americans who age into Medicare have the option to delay Part B enrollment, individuals who do make that choice need to proceed with caution to avoid enrollment penalties that could continue indefinitely.

What is the Medicare Part B Special Enrollment Period (SEP)?

The Medicare Part B SEP allows people to delay Part B enrollment if they have health coverage through their own employer or a spouse’s current employer. While coverage that isn’t through current employment – such as COBRA benefits, retiree or individual-market coverage – does not count for the purposes of this SEP, you may still qualify if your employment ended recently.

You’ll definitely want to sign up for Part B if you’re covered by a small employer that has fewer than 20 employees (100 employees if you have Medicare due to a disability). Medicare is your primary insurer in this situation, and your employer plan may pay less for your care – or pay nothing at all – if it finds out you are Medicare-eligible.

People who are covered through larger employers (20 or more employees if you qualify for Medicare based on age, 100 or more employees if you qualify based on disability) occasionally choose to enroll in Part B in addition to their employer plan, because Medicare can cover the job-based plan’s out-of-pocket costs.

Do I qualify for the Medicare Part B Special Enrollment Period?

You qualify for the Part B SEP if:

  • you are eligible for Medicare because of your age or because you collect disability benefits. (People who have ESRD Medicare are excluded.);
  • you had Medicare Part B or current job-based group health coverage in the month you qualified for Medicare; and
  • less than eight months have elapsed since you didn’t have either current job-based group health coverage or Medicare Part B.

How do I use the Part B SEP?

To use this SEP you should call the Social Security Administration (SSA) at 1-800-772-1213 and request two forms: CMS 40B (Medicare enrollment request) and CMS L546 (Request for employment information). You’ll complete the Medicare enrollment application and give the request for employment information form to your employer (or your spouse or family member’s employer, if applicable). You’ll request additional copies of form L564 from SSA if you’ve been covered through more than one job-based plan since you became Medicare eligible.

You should document the phone call with SSA and keep copies of the enrollment forms once you submit them in case you need to follow up. If your enrollment request is denied, you’ll have the chance to appeal.

While people 65 and older only qualify for this SEP if they have coverage through their own or a spouse’s job, disabled individuals under 65 also can qualify if they’re covered through a non-spouse family member’s job-based insurance.

You can delay your Part B effective date up to three months if you enroll while you still have job-based coverage or within one month after that coverage ends. Otherwise, your Part B coverage will begin the month after you enroll.


Josh Schultz has a strong background in Medicare and the Affordable Care Act. He managed a Medicare ombudsman contract at the Medicare Rights Center in New York City, and represented clients in extensive Medicare claims and appeals.

In addition to advocacy work, Josh helped implement federal and state health insurance exchanges at the technology firm hCentive. He also has held consulting roles, including as an associate at Sachs Policy Group, where he worked with insurer, hospital and technology clients on Medicare and Medicaid issues.

Contributions to healthinsurance.org and medicareresources.org represent only his own views.

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