Medicare Effective Dates: When Does Your Coverage Start?
Your Medicare effective date depends on when you enroll and which Medicare enrollment period you’re using.
Medicare Enrollment Checklist: Documents and Steps You Need
Last Modified: 10/05/2026 | Reviewed by Keith Armbrecht (NPN 634015)
Quick Summary
Starting Medicare is easier when you know which enrollment period applies, when your current insurance ends, and what information Social Security may need.
People simply turning 65 may be able to enroll online with relatively little paperwork.
People enrolling after 65 because employer coverage is ending may need additional proof of employer insurance.
Use this checklist before submitting your Medicare application.
Key Facts
Medicare Enrollment Checklist
- Confirm Your Medicare Eligibility Date
Know:
The month you turn 65
or
The date your qualifying employer insurance will end
if you’re retiring after 65.
- Determine Whether You’re Already Automatically Enrolled
If you’re already receiving qualifying Social Security benefits before age 65, you may be automatically enrolled in Medicare Parts A and B.
Check before submitting another application.
- Decide Whether You Need Part A, Part B or Both
Most people beginning Medicare use both.
Someone working after 65 may already have Part A but still need to apply for Part B.
- Have Your Basic Personal Information Available
Be prepared with information Social Security may need, such as:
- Social Security number
- Date and place of birth
- Current address
- Employment information
- Current health insurance information
- Know Your Employer Coverage Dates
If you’re retiring after age 65, know exactly:
When employment ends
and
when health coverage ends.
These dates aren’t always the same.
- Gather Employment-Coverage Documentation if Needed
People applying for Part B through the employer-based Special Enrollment Period may use:
CMS-40B
Application for Enrollment in Medicare Part B
and:
CMS-L564
Request for Employment Information
SSA also offers an online Special Enrollment Period application.
- Request Your Desired Part B Effective Date
If you’re transitioning from employer coverage, coordinate the Medicare date carefully to avoid a gap.
- Decide Between Original Medicare and Medicare Advantage
Once Part A and Part B are arranged, determine how you want to receive your healthcare coverage:
Original Medicare
or
Medicare Advantage
- If Choosing Original Medicare, Compare Medigap
Compare options such as:
- Plan G
- Plan N
- High Deductible Plan G
- Choose Prescription Drug Coverage
If using Original Medicare, evaluate Part D based on your:
- Prescriptions
- Dosages
- Pharmacy
- Formulary
- Premium
- Deductible
- Expected annual cost
- Verify All Effective Dates
Make sure:
Medicare Part A
Medicare Part B
Medigap or Medicare Advantage
and
Part D
begin when intended.
Video Explanation from Keith
Medicare Enrollment Checklist: Don’t Miss These Steps
Keith's Take
The Medicare application isn’t usually complicated.
Coordination is where people make mistakes.
I want four dates written down:
Last day of work
Last day of employer insurance
Part B effective date
Date your new Medicare coverage begins
If those dates line up correctly, you’ve eliminated a lot of potential problems.
Keith Armbrecht
Medicare on Video
Frequently Asked Questions
Q. What documents do I need to apply at 65?
A. A standard online Medicare application may require basic identity, employment and insurance information rather than extensive paperwork.
Q. What if I'm retiring after 65?
A. You may need documentation of qualifying employer coverage.
Q. What is CMS-40B?
A. The Application for Enrollment in Medicare Part B.
Q. What is CMS-L564?
A. The Request for Employment Information used in many employer-based Special Enrollment Period situations.
Q. Can I enroll online?
A. Yes, Social Security offers online Medicare enrollment options.
Q. Do I enroll in Plan G through Social Security?
A. No. Social Security handles Part A and Part B. Medigap is purchased separately from private insurers.
Q. Is Part D included with Original Medicare?
A. No. You generally add a separate Part D plan.
Official Government Sources
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