Form CMS-40B, Application for Enrollment in Medicare Part B
Form CMS-40B signs you up for Medicare Part B, the medical insurance half, most often used by people who delayed Part B while covered through work and are now enrolling.
This is the genuine CMS PDF, unmodified. Source: CMS official page.
What is CMS-40B?
Form CMS-40B applies for Medicare Part B, which covers doctor visits, outpatient care, and preventive services for a monthly premium. The classic filer already has premium-free Part A and skipped Part B because employer group coverage made it unnecessary; when that employment coverage ends, this form plus Form CMS-L564 from the employer claims the Special Enrollment Period that avoids the lifetime late enrollment penalty.
It is also used in the General Enrollment Period by people who missed their windows. The completed form goes to the Social Security Administration, which handles Medicare enrollment, by mail, fax, or upload; SSA also accepts online Part B enrollment for SEP cases.
Who files CMS-40B?
- People leaving employer coverage who delayed Part B, with a CMS-L564 attached
- Anyone enrolling during the January to March General Enrollment Period
- Part A beneficiaries adding Part B for the first time
How to fill out CMS-40B
- Fill in your name, Medicare number, and contact details.
- Enter the enrollment date you are requesting where applicable.
- If claiming a Special Enrollment Period, have your employer complete Form CMS-L564 as evidence of group coverage.
- Download, sign, and submit both forms to your local Social Security office by mail, fax, or its document upload service.
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Frequently asked questions
What is the late enrollment penalty I keep hearing about?
Part B premiums rise 10% for each full 12-month period you could have had Part B but did not, and the increase lasts as long as you have Part B. The employment-based Special Enrollment Period is how most people avoid it.
When does coverage start?
In a Special Enrollment Period, generally the month after SSA processes the enrollment, or you may choose a start within the rules; in the General Enrollment Period, the month after you sign up.