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.

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

Reviewed by our health policy panel.

Key takeaways

Although Americans who age into Medicare have the option to put off enrolling in Part B, 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 you to delay taking Part B if you have coverage through your own or a spouse’s current job. You usually have 8 months from when employment ends to enroll in Part B. Coverage that isn’t through a current job – such as COBRA benefits, retiree or individual-market coverage – won’t help you qualify for this SEP, but the SEP lasts for 8 months, so you may still qualify if your employment ended recently.

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 employment-based 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.

Some people may need to use the Part B SEP if they’re still working. You’ll want to sign up for Part B if your employer has less than 20 employees. This is because your employer plan pays only after Medicare does. If you don’t enroll in Part B, your employer plan will pay less for your care – or nothing at all – when it finds out you’re Medicare-eligible. If your employer has more than 20 employees, you don’t have to take Part B as long as you’re still working, but a small number of people do enroll to lower their out-of-pocket costs. (If you have Medicare because of a disability, you’ll need to enroll in Part B if your employer has less than 100 employees.)

You have to take Part B once your or your spouse’s employment ends. Medicare becomes your primary insurer once you stop working, even if you’re still covered by the employer-based plan or COBRA. If you don’t enroll in Part B, your insurer will “claw back” the amount it paid for your care when it finds out. At that point, you would need to enroll in Part B, but might no longer qualify for the SEP if you delayed enrolling for more than 8 months.

(Enrolling in Medicare when you already have COBRA will cause the COBRA coverage to end. If this happens, your spouse and any dependents can continue coverage under the COBRA plan, even though you are no longer covered.)

How do I use the Part B SEP?

To use this SEP you should call the Social Security Administration at 1-800-772-1213 and request two forms: the Part B enrollment request form (CMS 40B) and the request for employment information form (CMS L564). You’ll complete the Medicare enrollment application and give the request for employment information form to the employer to fill out. You want to request additional copies of form L564 from Social Security if you’ve been covered through more than one job-based plan since you qualified for Medicare.

If an employer is unable to fill out the form, Social Security may accept the following items as evidence you had job-based coverage:

  • Income tax forms showing you paid health insurance premiums;
  • W-2s or pay stubs showing pre-tax medical insurance premiums withheld;
  • health insurance cards with a policy effective date;
  • explanations of benefits; or
  • statements or receipts showing you paid health insurance premiums.

You should write down what you talk about with Social Security, and keep copies of the enrollment forms you submit in case you need to follow up. If your enrollment request is denied, you’ll have the chance to appeal.

People 65 and older only qualify for this SEP if they have coverage through their own or their spouse’s job, but disabled individuals can also qualify because they’re covered by a non-spouse family member’s plan.

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

What if an employer gives me money to buy my own health plan?

A note about individual coverage: you’ll qualify for an SEP if you delayed Part B because you had employer-sponsored coverage through a group health plan (GHP). This is a specific type of insurance plan sponsored or run by your employer. It includes coverage your employer offers you through an insurer, and plans purchased from the Small Business Health Options Program (SHOP) marketplace.

Instead of offering GHP coverage, some employers provide you money to buy your own health insurance. They can reimburse you directly, in which case the money is taxed, or through a Qualified Small Employer Health Reimbursement Arrangement (QSEHRA) or an Individual Coverage Health Reimbursement Account (ICHRA). Coverage you buy on your own does not qualify you for the Part B SEP – even if an employer paid for some or all of it. If you have individual coverage, you should sign up for Medicare when you’re first eligible, and can enroll during your initial enrollment period or the general enrollment period.


Josh Schultz has a strong background in Medicare and the Affordable Care Act. He coordinated 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 worked on federal and state health insurance exchanges at the technology firm hCentive.

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

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