CMS-40B Customer-Assembly Preparation Kit
This workflow helps you prepare a Medicare Part B enrollment application for the applicant to finish and submit. PostalForm prepares the official form and delivers the unsigned preparation kit only to your verified address. PostalForm does not file, serve, or submit it. Hand-sign and date CMS-40B, add a completed employer-signed CMS-L564 or other accepted proof when using a Special Enrollment Period, verify the enrollment window, and submit the final package to the local Social Security office yourself.
PostalForm prepares and prints an unsigned customer-assembly kit and sends it only to your verified address. You perform final assembly and submission.
PostalForm is not affiliated with Centers for Medicare & Medicaid Services.
Need more context?
The form is ready to fill now. If you want supporting instructions, mailing notes, or source links, they are below.
Important details+
Answer the guided questions and PostalForm prepares the official form, leaves signature areas blank, adds a customer instruction cover, and sends the packet only to your verified address. Nothing is filed or submitted for you. Hand-sign and date CMS-40B, add a completed employer-signed CMS-L564 or other accepted proof when using a Special Enrollment Period, verify the enrollment window, and submit the final package to the local Social Security office yourself.
What you need+
- Your Medicare number (you must already have Part A)
- Name, mailing address, phone, and email
- Dates of job-based (or volunteer) health coverage since you turned 65, if any
- Form CMS-L564 or other proof of coverage for a Special Enrollment Period
- Signature and date
- Hand-sign the printed form after the preparation kit is delivered
- CMS-L564 or other proof of job-based coverage (for a Special Enrollment Period) (optional) — If you are using the Special Enrollment Period, include Form CMS-L564 (Request for Employment Information) completed by each employer - or other proof such as W-2s, pay stubs, health insurance cards, or benefit statements. Send copies, never originals.
- Extra pages or documentation (optional) (optional) — Attach a separate sheet if you need more room for coverage dates, or the letter or notice that asked you to enroll in Part B (question 4).
Form summary+
This workflow helps you prepare a Medicare Part B enrollment application for the applicant to finish and submit. PostalForm prepares the official form and delivers the unsigned preparation kit only to your verified address. PostalForm does not file, serve, or submit it. Hand-sign and date CMS-40B, add a completed employer-signed CMS-L564 or other accepted proof when using a Special Enrollment Period, verify the enrollment window, and submit the final package to the local Social Security office yourself.
How it works+
- Answer the guided questions and review the prepared form information.
- PostalForm prints the official form with signature areas left blank and sends the customer-assembly kit only to your verified address.
- After delivery, follow the cover instructions, hand-sign where required, and add every original, certified record, payment, witness, certification, companion form, or other physical item.
- Verify the current deadline and destination, then personally complete final submission through the official channel.
Where it gets mailed+
PostalForm mails the unsigned preparation kit to you. You complete the signatures, physical enclosures, and final submission yourself.
Packet order+
- Customer assembly instruction cover (remove and keep before final submission)
- Prepared unsigned form (signature and reserved third-party fields blank)
- Printed reference attachments
Common mistakes+
- Using CMS-40B without having Part A yet - first-time Medicare applications go through Social Security, not this form.
- Missing the 8-month Special Enrollment Period window after job-based coverage or employment ends.
- Counting COBRA or retiree coverage as job-based coverage - they do not qualify you for a Special Enrollment Period.
- Skipping Form CMS-L564 (or other proof of coverage) when enrolling through a Special Enrollment Period.
- Mailing the form to a national Medicare address instead of your local Social Security office.
FAQs+
Where do I mail Form CMS-40B?
To your local Social Security office - there is no national address. Find yours with the Social Security office locator at secure.ssa.gov/ICON or call 1-800-772-1213. You can also fax the signed form to 1-833-914-2016.
Can I sign up for Medicare Part B online instead of mailing this form?
Usually, yes. If you already have Part A, you can apply at ssa.gov/medicare/sign-up and upload your proof of coverage. Mailing the paper CMS-40B is right for people who prefer paper or cannot use the online application.
Do I also need Form CMS-L564?
Only if you are enrolling through a Special Enrollment Period based on job coverage. Each employer whose coverage you are counting should verify it on Form CMS-L564 - or you can include other proof, like W-2s, pay stubs, health insurance cards, or benefit statements.
When will my Part B coverage start?
Generally the first day of the month after Social Security processes your enrollment. If you are still covered by a job-based plan (or within the first full month after it ends), the form lets you choose a start month up to 3 months after you enroll.
What is the Part B late enrollment penalty?
Usually an extra 10% of the standard premium for each full 12-month period you could have had Part B but did not sign up - and it lasts for as long as you have Part B. Enrolling during your Initial or Special Enrollment Period avoids it.
Does COBRA or retiree coverage count for the Special Enrollment Period?
No. The Special Enrollment Period is based on current employment. Your 8-month window starts when the employment or the active-employment coverage ends, whichever comes first - COBRA and retiree plans do not extend it.
Sources+
Last verified+
Last Centers for Medicare & Medicaid Services verification: July 12, 2026