CMS (Centers for Medicare & Medicaid Services) · United States

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Form CMS-40B: Request for Enrollment in Medicare Part B (Medical Insurance)

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Quick answer

Form CMS-40B, Request for Enrollment in Medicare Part B (Medical Insurance) — titled Application for Enrollment on earlier editions and HCFA-40B under the agency's former name — is the CMS form for people who already have Medicare Part A and want to add Part B: during the Initial Enrollment Period, the General Enrollment Period (January 1 to March 31 each year) or a Special Enrollment Period after employer or union coverage ends. The current edition is CMS-40B (07/2025), a free fillable PDF from cms.gov. You fax or mail the signed form to your local Social Security office, with Form CMS-L564 completed by the employer when you claim a Special Enrollment Period; if you are ending an employer group plan, Social Security also accepts the application online. With JustFill you upload the blank CMS-40B PDF, the AI maps each field, you type or dictate your answers, and the first clean completed PDF download is included at no charge.

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Form CMS-40B
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CMS (Centers for Medicare & Medicaid Services)
Country
United States
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Official edition
CMS-40B (07/2025), "Request for Enrollment in Medicare Part B (Medical Insurance)", OMB No. 0938-1230, expires 07/31/2028; the CMS form page lists revision date 2025-07-01
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What is Form CMS-40B?

CMS-40B enrolls you in Medicare Part B when you already have Part A — most often because you delayed Part B while you or your spouse had group health coverage through current employment. The July 2025 edition is two pages plus an instruction page: Section 1 asks for your Medicare Number, name, mailing address, phone and email; Section 2 asks whether you had employer or union coverage since turning 65, the dates of that employment and coverage (which your employer confirms on Form CMS-L564, Request for Employment Information, returned with the application), whether anyone is requiring you to enroll, and which month you want coverage to start; Section 3 is your signature, with a witness only if you sign by mark. If you do not have Part A, the form tells you not to use it and to contact Social Security to apply for Medicare for the first time. JustFill lets you complete the CMS-40B online so your Medicare Number and dates are legible before you fax or mail it to your local Social Security office.

Download the Form CMS-40B form PDF — free

The official CMS-40B (07/2025) is a free three-page PDF from CMS at cms.gov/medicare/cms-forms/cms-forms/downloads/cms40b-e.pdf (instructions on page 1, the form on pages 2–3), listed on the CMS forms page as revision date 2025-07-01. It is already a fillable PDF, so there is nothing to buy or "unlock": fill it in Acrobat Reader, or open the same blank in JustFill to type or dictate every field in any browser — the first clean completed PDF download is included at no charge. Print it, sign by hand, and fax or mail it to your local Social Security office (ssa.gov/locator), with Form CMS-L564 if you are using a Special Enrollment Period.

Get the official Form CMS-40B PDF from CMS (Centers for Medicare & Medicaid Services)

Who fills out Form CMS-40B?

  • People with Medicare Part A who delayed Part B and now want to enroll
  • Beneficiaries enrolling during a Special Enrollment Period after employer coverage ends
  • Those signing up during the Medicare General Enrollment Period
  • Anyone pairing Part B enrollment with Form CMS-L564 to avoid a late penalty

Field-by-field breakdown

What each section of Form CMS-40B asks for. JustFill’s AI will detect these fields automatically when you upload the PDF — review the breakdown below so you know what to enter.

Section 1 — Basic information (items 1–5)

Your Medicare Number exactly as printed on your card, first, middle and last name with suffix, mailing address, phone number and email address. The form says all fields are required unless noted.

Section 2, items 1–3 — Employer coverage and dates

Whether you have (or had) coverage through an employer or union group health plan since turning 65, whether you were an international volunteer with non-profit health coverage, and — if either is Yes — the start and end dates (mm/yyyy, or "Not ended") of the employment, the volunteer work and the health coverage. Your employer completes Form CMS-L564 to confirm the same dates.

Section 2, item 4 and coverage start date

Item 4 asks whether an employer, insurer or other entity has asked or required you to enroll in Part B — if Yes, explain and attach proof. Then choose when coverage starts: if you enroll while still covered by the group plan or in the first full month after it ends, you may pick the first day of the month you enroll or the first day of any of the following three months.

Section 3 — Signature(s)

Your signature and the date (mm/dd/yyyy). If you sign by mark (X), a witness who knows you must also print their name, sign and date.

Common mistakes to avoid

  • 1Submitting CMS-40B without Form CMS-L564 when claiming a Special Enrollment Period — the employer proof is usually required.
  • 2Using this form when you do not yet have Part A — it says to contact Social Security to apply for Medicare for the first time instead — or entering a Medicare Number that does not match your card exactly.
  • 3Missing the enrollment window, which can cause a lifelong Part B late-enrollment penalty.

Form CMS-40B example — what a filled-out form looks like

A fictional retiree, Pat Example, has had Medicare Part A since turning 65 in 2021 but stayed on a spouse's employer plan. That plan ended in June 2026, so Pat is enrolling in Part B during the Special Enrollment Period.

Section 1, item 1 — Medicare Number

1EG4-TE5-MK••

Masked on purpose. Copy the 11-character number exactly as printed on your red, white and blue Medicare card.

Section 1, items 2–3 — Name and mailing address

PAT EXAMPLE — 100 Sample Street, Austin, TX 78701

Use the name shown on your Medicare card; the address is where Social Security will write to you.

Section 1, items 4–5 — Phone and email

(555) 010-0199 — pat@example.com

The form marks all fields as required unless noted, and Social Security may call with questions.

Section 2, item 1 — Employer or union group health plan since 65?

Yes

Answering Yes triggers item 3 and is what makes this a Special Enrollment Period request.

Section 2, item 2 — International volunteer?

No

Only for people who were covered while volunteering abroad for a non-profit.

Section 2, item 3 — Dates of employment and coverage

Spouse worked for the employer 09/2001 – 06/2026; employer health coverage 09/2001 – 06/2026

Enter mm/yyyy. The employer confirms the same dates on form CMS-L564, which is returned with this application.

Section 2, item 4 — Asked or required to enroll in Part B?

No

Tick Yes only if an employer or insurer is making you enroll, and attach the proof the form asks for.

Choose your coverage start date

The first day of the month you enroll

Because the enrollment falls within the first full month without the group plan, the form lets you pick this or the first day of any of the next three months.

Section 3 — Signature and date

PAT EXAMPLE — 09/02/2026

Sign by hand before faxing or mailing. A witness signs items 3–5 only if the applicant signs with a mark (X).

These values are made up. They are here to show what belongs on each line, not to be copied — every name, number, and address on your own Form CMS-40B has to be your own.

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Related forms

CMS (Centers for Medicare & Medicaid Services)

CMS-L564

CMS-L564: Request for Employment Information (Medicare)

SSA (Social Security Administration)

Form SSA-44

Form SSA-44: Medicare Income-Related Monthly Adjustment Amount — Life-Changing Event

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Frequently asked questions

To sign up for Medicare Part B when you already have Part A. The form lists three windows: your Initial Enrollment Period, the General Enrollment Period from January 1 to March 31 each year, and a Special Enrollment Period — for example within eight months after employer or union group coverage based on current employment ends. If you have never enrolled in Medicare at all, do not use this form; apply for Medicare through Social Security instead.
Usually yes, if you are enrolling through a Special Enrollment Period — CMS-L564 proves the employer coverage that lets you avoid a late-enrollment penalty. JustFill can fill both.
Yes. The CMS PDF itself is fillable in Adobe Acrobat Reader, and JustFill opens the same blank in your browser: the AI detects each field, you type or dictate your Medicare Number, dates and answers, and the first clean completed PDF download is included at no charge. Print and sign it by hand before faxing or mailing — Social Security needs a signed copy.
Fax or mail the signed form to your local Social Security office — find it at ssa.gov/locator — or hand it in there in person. If you are enrolling because an employer group health plan is ending, Social Security also offers an online application (the "Start application" link at ssa.gov/medicare/sign-up/part-b-only), where you upload the completed CMS-40B and your employer's CMS-L564 or other proof of coverage. For the General Enrollment Period, Social Security asks you to call 1-800-772-1213. Fill it in JustFill first so the copy you fax or upload is legible.
Yes. The form kept its number when the Health Care Financing Administration (HCFA) became the Centers for Medicare & Medicaid Services (CMS) in 2001, so "HCFA 40B" and "CMS-40B" are the same Medicare Part B enrollment form. Use the current CMS-40B (07/2025) edition from cms.gov — older printouts titled "Application for Enrollment" carry an expired OMB date.

Official source: Form CMS-40B on CMS (Centers for Medicare & Medicaid Services)’s website

Edition checked: CMS-40B (07/2025), "Request for Enrollment in Medicare Part B (Medical Insurance)", OMB No. 0938-1230, expires 07/31/2028; the CMS form page lists revision date 2025-07-01. Verified against the official source on · Verified in our Government Forms Fillability Study.

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Form CMS-40B

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