✅Written by Dr. Ed Weir, Former SSA District Manager✓ Verified March 2026
CMS-40B & CMS-L564 Form Walkthrough
START HERE
You're Not Alone in This
Take a deep breath. You're about to enroll in Medicare Part B, and it feels like a lot of paperwork. That's normal. This guide will walk you through every field, explain what it means, and show you exactly what to write. By the end, you'll have two completed forms ready to mail.
This guide covers two forms that always go together:
CMS-40B: Your Medicare Part B enrollment application
CMS-L564: Your proof of employer health insurance coverage
Why This Matters
If you lost your job or your employer's health insurance ended, you have an 8-month window to sign up for Medicare Part B without paying an extra 10% surcharge forever. CMS-L564 proves to Medicare that you had coverage, so they won't penalize you. That's why both forms are critical.
What you'll need:
Your Medicare card
Your Social Security number
Your employer's name and address
Dates your coverage started and ended
Your employer's contact info (they'll need to sign Section B)
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SECTION 1 OF 5
Your Name & Medicare Number
This is the easiest part. You're just telling Medicare who you are.
Your Full Name
Text Field
Write your name exactly as it appears on your Social Security card. First, middle (if you have one), and last name.
Example:
John Q. Public
Why This Matters
If your name doesn't match exactly, SSA will ask for a new form. Use your legal name, not a nickname.
Your Medicare Claim Number
11-Character Code
Look at the top left of your Medicare card. It's usually 9 numbers, a hyphen, 2 numbers, a hyphen, and 2 numbers OR 10 numbers followed by a letter. It's NOT your Social Security number.
Example:
000-00-0000A
Tips
Your Medicare card is different from your Social Security card
Include the letter at the end if your card has one
If you can't find your card, call SSA at 1-800-772-1213
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SECTION 2 OF 5
Where You Live
SSA uses this address to mail you important documents, so accuracy matters.
Street Address
Text Field
Your current home address. Spell out the full street name (for example, "Street" not "St"). Do not use a PO Box.
Example:
123 Main Street
City, State, ZIP Code
Text Fields
Your city (spelled out), state abbreviation (CA, TX, FL, etc.), and full 5-digit ZIP Code.
Example:
Anytown, CA 12345
Tips
Spell out the city (no abbreviations)
Use the 2-letter state code
ZIP Code must be at least 5 digits
Your Phone Number
Text Field
10-digit number with area code. SSA might call with questions, so use a number where you can be reached.
Example:
(555) 123-4567
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SECTION 3 OF 5
Why Are You Signing Up Now?
Why This Matters
Your answer here determines if you qualify for a Special Enrollment Period (SEP), which means no penalty even if you missed the initial sign-up window.
Reason for Enrollment
Checkbox (Check Only One)
If you lost your job or your employer's health insurance ended, check: "I am applying during a Special Enrollment Period."
Key Options
If you lost employer coverage → "Special Enrollment Period"
If you're over 65 and this is your first time → "I already have Part A"
If you're applying in Jan–Mar → "General Enrollment Period"
Have You Been Employed Since You Turned 65?
Checkbox (Yes/No)
If you worked AFTER you turned 65 and had employer health insurance, check "Yes." This triggers the employer coverage question and makes CMS-L564 required.
Important
Include your spouse's employment if married
Self-employment counts (1099 income)
Even part-time or seasonal work counts
If "Yes," you MUST provide employer details below
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SECTION 4 OF 5
Your Employer Details (You Fill This)
Gather your last paystub, W-2, or benefits paperwork. You're filling in facts about your employer and when your coverage ended.
Employer's Name
Text Field
Legal name of your employer (from your W-2 or paystub). Include "Inc.," "LLC," or "Corp." if that's how it's officially named.
Example:
ABC Corporation
Employer's Address
Text Field
Employer's main office or benefits office address (not your home address). Look on your paystub or benefits paperwork.
Example:
456 Corporate Boulevard, Anytown, CA 12345
When You Worked (Employment Dates)
Text Field (Date Range)
Start and end dates of your employment. Format: MM/DD/YYYY – MM/DD/YYYY
Example:
01/15/2010 – 12/31/2026
Tips
Include the full month, day, and year
If still employed, write "still employed" or today's date
Check your first paystub and last paystub for exact dates
When Your Health Coverage Was Active
Text Field (Date Range)
When the employer's group health plan covered you. This may be DIFFERENT from employment dates (there's often a waiting period). Format: MM/DD/YYYY – MM/DD/YYYY
Example:
02/15/2010 – 12/31/2026
Important
Coverage often starts 30–90 days after hire
Include any COBRA coverage or continuation coverage if applicable
Check benefits enrollment letter or pay stub for coverage end date
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SECTION 5 OF 5
When Should Part B Coverage Start?
Why This Matters
This date affects when your coverage begins and whether you stay in your 8-month Special Enrollment Period window.
Desired Coverage Start Date
Date Field (MM/DD/YYYY)
The first day you want Medicare Part B to cover you. Usually the 1st of a month.
Example:
01/01/2026
Rules
Use the first day of a month when possible
For Special Enrollment Period: earliest start is the month your coverage ended
Latest start: usually 3 months after you apply
Cannot start before you turn 65
🚨 The 8-Month Window
You have 8 months from the date your employer coverage ended to sign up without a penalty. Miss this window and you'll owe 10% extra per 12-month period forever. That's why CMS-L564 (Section B, signed by your employer) is critical—it proves you had coverage during the window.
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FINISHING CMS-40B
Sign Your Form
You're almost done with the first form. A signature is required—SSA won't process unsigned forms.
Your Signature
Signature Line
Sign your name in cursive or in your usual signature. Use blue or black ink. Do NOT print your name or type it.
If You Can't Sign
You can mark with an "X"
A witness must then sign next to your X and print their name
Unsigned forms are rejected
Date You Signed
Date Field (MM/DD/YYYY)
The date you physically signed the form (today or recently). Must be on or before the date you mail it.
Example:
03/06/2026
Checkpoint: CMS-40B is now complete!
You've finished the first form. Next, you'll fill out CMS-L564 Section A (about your employer), then give it to your employer to sign Section B.
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STARTING CMS-L564
Proof of Employer Coverage (Part 1: You)
CMS-L564 has two sections. You fill Section A. Your employer fills Section B. Both are needed to waive the late enrollment penalty.
Why This Form Matters
CMS-L564 proves to Medicare that you had employer health insurance when your Part B enrollment period ended. Without it, SSA will charge you a 10% surcharge forever. With it, you're protected.
Two-Part Process:
Section A (This section): You complete your information and employer details
Section B (Next section): Your employer certifies employment and coverage dates
🚨 Critical: Your Employer Must Sign Section B
After you fill Section A, you MUST give this form to your employer's HR or benefits department. They will complete and sign Section B. This is not something you can fill in yourself—SSA will only accept Section B if signed by an authorized company official.
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CMS-L564 SECTION A
Your Information
Most of this mirrors CMS-40B. If you use the same information, that's correct.
Your Name
Text Field
Same as CMS-40B. Legal name exactly.
Example:
John Q. Public
Your Social Security Number
Text Field
9-digit SSN. Same as CMS-40B.
Example:
000-00-0000
Your Medicare Number
Text Field
Same Medicare claim number from CMS-40B.
Example:
000-00-0000A
Employer's Name
Text Field
Same employer name from CMS-40B. Legal name exactly.
Example:
ABC Corporation
Employer's Address
Text Field
Same address from CMS-40B. Full street address, city, state, ZIP.
Example:
456 Corporate Boulevard, Anytown, CA 12345
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CMS-L564 SECTION A (CONT.)
Employment & Coverage Details
You're summarizing the key facts about your employment and coverage. Your employer will verify these in Section B.
Employment Dates
Text Field (Date Range)
From when you started to when you ended employment. Same as CMS-40B Item 3.
Example:
01/15/2010 – 12/31/2026
Tip
If still employed: write "still employed" or leave end date blank
Group Health Plan Coverage Dates
Text Field (Date Range)
When the employer's health insurance covered you (may be different from employment dates). Same as CMS-40B Item 3.
Example:
02/15/2010 – 12/31/2026
Key Point
Coverage may have started after hire (waiting period)
May have ended after employment (COBRA or severance coverage)
Be precise—these dates matter for the SEP window
Type of Coverage You Had
Checkbox
Check the coverage level: self-only, employee + spouse, employee + child(ren), or family.
Example
If you were insured alone: "Self-only." If your spouse and children were also covered: "Family."
Why This Matters
These dates are the heart of your SEP case. Employer Section B will confirm them. Accuracy here prevents delays.
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CMS-L564 SECTION B
Your Employer Fills This (NOT You)
🚨 IMPORTANT: Do NOT Fill Section B Yourself
Section B must be completed and signed by your employer's HR or benefits department. If you or anyone other than an authorized company official signs Section B, SSA will reject it.
What Your Employer Will Do:
Confirm your employment dates match their records
Confirm when your group health coverage started and ended
State whether you're still covered or if coverage ended
State whether your coverage is being terminated
Sign the form with their job title and company phone number
How to Get Section B Signed
Action Items
Print Section A (after you fill it out)
Sign CMS-L564 Section A yourself
Take or mail it to HR/Benefits at your (former) employer
Ask them to complete Section B within 10 business days
Request they email or mail it back to you
What Section B Fields Ask
Confirm employment dates
Confirm group health plan coverage dates
Is employee still covered? (Yes/No with end date if No)
Is group coverage being terminated? (Yes/No with date if Yes)
Official signature, title, and phone number
Why Section B Is Critical
Medicare verifies all dates through this section. Without the employer's signature and confirmation, SSA has no proof you had coverage. That means they might charge the 10% penalty. That's why you need to follow up with HR to make sure they send it back quickly.
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FINAL STEPS
Submit Your Forms & Follow Up
✓ You've Got This
Both forms are complete (CMS-40B signed by you, CMS-L564 Section A signed by you, and Section B signed by your employer). Now you're ready to submit.
Submission Checklist
Before You Mail
☐ CMS-40B is signed and dated
☐ CMS-L564 Section A is filled in and signed by you
☐ CMS-L564 Section B is filled in and signed by employer
☐ All dates match between the two forms
☐ Employer phone number is on CMS-L564 Section B
☐ You've kept a copy for your records
Where to Submit
Mailing Address
Option 1: Mail to your local Social Security office
Bring the forms to your local SSA office. Take a number and wait your turn.
After You Submit
What to Expect
2–4 weeks: SSA processes your form
Confirmation: You'll receive a letter from SSA confirming Part B enrollment and your effective date
Your Medicare card: A new card showing Part B will arrive by mail
💡 Important Reminder
You have 8 months from the date your employer coverage ended to enroll without a penalty. If you're within that window, CMS-L564 protects you. If you're past 8 months, the penalty applies automatically unless you have another valid SEP reason (such as loss of coverage due to employer plan termination, not just job loss).
Social Security questions: Call 1-800-772-1213 | TTY 1-800-325-0778
Hours: Monday–Friday, 7 a.m.–7 p.m. your local time
Need Help with Medicare Part B Enrollment?
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