How to Enroll in Medicare Parts A and B
Social Security handles Parts A and B. The correct path depends on whether enrollment is automatic, you need both parts or you already have Part A.
Apply for Medicare Parts A and B through the Social Security Administration. Railroad Retirement beneficiaries generally work through the Railroad Retirement Board. Medicare Advantage, Medigap and Part D are separate decisions made after the underlying Medicare dates are established.
Which Application Fits Your Situation?
First-time Parts A and B
Use Social Security’s Medicare application if you are not enrolled and want both parts, or Part A only.
Already have Part A
Use the Part B-only process. A working-aged SEP applicant may also need proof of current-employment coverage.
Automatic enrollment
If a Medicare card arrives automatically, verify the dates and follow the official instructions before declining Part B.
If you are unsure whether a card should arrive automatically, start with Will I Be Automatically Enrolled in Medicare at 65?
Complete the Application Without Guessing
Calculate the desired start date
Use the Initial Enrollment Period guide or the applicable Special Enrollment Period. Do not choose a date based only on when an employer plan is expected to end.
Gather identifying and coverage information
Prepare your Social Security information, contact details, current insurance dates and any employer documentation needed for an SEP.
Apply through the official channel
Social Security offers online Medicare applications and Part B-only enrollment. Fax, mail, phone or office options may also be available depending on the application.
Save confirmation and verify approval
Keep copies, confirmation numbers and submitted forms. Verify the approved effective dates rather than relying only on the date requested.
When CMS-40B and CMS-L564 Enter the Process
Someone who already has Part A and enrolls in Part B after current-employment coverage commonly uses CMS-40B together with CMS-L564. CMS-40B requests Part B. CMS-L564 documents employment and group health coverage.
Contact Social Security about alternative evidence. Social Security—not the employer, plan or broker—decides whether the SEP requirements are met.
See the dedicated Part B Special Enrollment Period and forms guide.
Enrollment in A and B Does Not Complete the Coverage Decision
After the dates are established, compare Medicare Advantage with Original Medicare plus any Medigap and Part D coverage. Consider doctors, prescriptions, travel, costs and the Medigap enrollment window. Visit the Turning 65 Medicare guide for that broader comparison.
Frequently Asked Questions
Can a Medicare broker submit my Parts A and B application?
No. Social Security or the Railroad Retirement Board handles Parts A and B enrollment.
Do I need to start Social Security retirement benefits to get Medicare?
No. You can apply for Medicare without starting monthly retirement benefits.
What if I already have Part A?
Use the Part B-only enrollment process. If you are using the working-aged SEP, proof of current-employment coverage may also be required.
How long does the application take?
Processing time varies. Apply early enough for your situation, keep confirmation and verify the approved dates before other coverage ends.
Can I enroll in Medicare Advantage through Social Security?
No. Social Security establishes Parts A and B. Medicare Advantage and Part D enrollment occurs separately through Medicare, the plan or an authorized agent or broker.
Sources and Enrollment Resources
Establish Medicare Before Comparing the Private Coverage
Once Parts A and B are approved, Benjamin Thompson can help compare the Medicare Advantage, Medicare Supplement and Part D options represented by Thompson Medicare Brokerage.
Thompson Medicare Brokerage is not connected with or endorsed by the U.S. government or the federal Medicare program. This page provides general educational information. Social Security or the Railroad Retirement Board makes official Medicare Parts A and B enrollment, effective-date and penalty decisions. Employer, Marketplace and tax consequences depend on individual circumstances.