What Do You Need to Do to Sign Up for Medicare?
Who Qualifies for Medicare? (Age, Disability, ESRD, and Work History Requirements)
Understanding Medicare eligibility is crucial when you prepare to sign up for Medicare. The program is available not only to those turning 65, but also to people under 65 who qualify due to certain disabilities or End-Stage Renal Disease (ESRD). Eligibility is determined by several factors, including age, disability status, work history, and citizenship or lawful residency status.
Medicare Eligibility by Age
If you are age 65 or older, you generally qualify for Medicare if you are a U.S. citizen or a lawful permanent resident with at least five continuous years of residency. Premium-free Part A is available if you (or your spouse or qualifying parent/child) have worked and paid Medicare taxes (FICA) for at least 40 quarters, also called Quarterly Credits (QCs). In most cases, receiving Social Security or Railroad Retirement Board (RRB) benefits means you will be automatically eligible for Parts A and B. For more on RRB-specific details, visit What Is Railroad Medicare? Eligibility, Costs, and Benefits.
Medicare for People Under 65
- Disability: If you are under 65 and have a qualifying disability, you become eligible for Medicare after receiving Social Security Disability Insurance (SSDI) payments for 24 months. For certain former government employees not covered by Social Security, the waiting period is 29 months. Those with Amyotrophic Lateral Sclerosis (ALS) qualify immediately, with no waiting period.
- ESRD (End-Stage Renal Disease): Medicare is available at any age if you have permanent kidney failure requiring regular dialysis or a kidney transplant. Coverage typically begins the third month after a regular course of dialysis starts, or earlier with home dialysis training or a transplant.
- Eligibility for ESRD Medicare depends on work history or having a spouse/parent/child with sufficient FICA credits or eligibility for Social Security/RRB benefits.
Work History Requirements
For premium-free Part A, you usually need 40 quarters of Medicare-covered employment (10 years). If you have fewer, you can still enroll in Part A but must pay a premium. Part B always requires a monthly premium, regardless of work history.
Visit our What Is CMS for Medicare? Key Functions and Role Explained guide to learn about Medicare’s administration and its relationship to Social Security, Railroad Retirement, and your work credits.
When Can You Enroll? Key Enrollment Periods
Knowing when you can enroll in Medicare is just as essential as meeting eligibility requirements. Enrolling during the correct period helps you avoid costly, permanent late enrollment penalties and ensures you receive timely coverage.
The Initial Enrollment Period (IEP)
Your main opportunity to enroll is the Initial Enrollment Period. For most, this is a seven-month window:
- Begins three months before your 65th birthday month
- Includes your birthday month
- Ends three months after your birthday month
If you’re under 65 and qualify by disability, your IEP starts three months before your 25th month of receiving SSDI or RRB disability benefits.
For ALS, Medicare begins the first month of SSDI benefits. For ESRD Medicare, enrollment is not automatic-academic medical centers and your kidney care team can guide you during the process.
Special Enrollment Periods (SEPs)
| SEP Type | Who Qualifies? | Window | Key Details |
|---|---|---|---|
| Working Aged/Disabled | Covered by current employer (yours/your spouse’s) | Anytime covered or up to 8 months after coverage/employment ends | Not available for ESRD; must file CMS-L564 |
| TRICARE | Under 65, disability/ESRD, prior TRICARE | Month after IEP or at notification | Special rules for military/retirees; see DOD/SSA details |
| Employer Misinformation | Given wrong details by employer/group plan | Upon documentation submission | Use CMS-10797 |
Learn more about signing up if you’re still working at 65 and your eligibility for Special Enrollment Periods.
General Enrollment Period (GEP) and Late Enrollment
If you miss your IEP and do not have a qualifying SEP, you can enroll January 1-March 31 each year, with coverage starting the month after you enroll. A late enrollment penalty may apply for both Part A and Part B, and your coverage could be delayed.
Step-by-Step: How to Apply for Medicare Parts A and B
Here’s your actionable, step-by-step guide for how to apply for Medicare:
- Check for Automatic Enrollment
- You’ll be automatically enrolled in Parts A and B if you’re already getting Social Security or RRB benefits at least four months before your 65th birthday (or after 24 months of SSDI/ALS).
- You’ll receive a Medicare card in the mail-no separate application needed.
- If You’re Not Automatically Enrolled: Apply Manually
- Apply for Medicare online Social Security at ssa.gov, by phone (1-800-772-1213), or in-person at your local SSA office.
- Complete the Social Security Medicare application or appropriate CMS forms (CMS-40B for only Part B, CMS-4040 for Medicare without Social Security/RRB, CMS-43 for ESRD, CMS-10797 for SEP due to misinformation).
- Have required documentation: Proof of age, citizenship/lawful residency, and work history (SSI/RRB verification or FICA reporting).
- Enroll in Part B if Needed
- Part B enrollment is required to get premium Part A or if not already included with your automatic coverage.
- Direct payment may be needed if not yet drawing Social Security.
- For People Under 65 (Disability or ESRD):
- Most will be automatically enrolled after 24 months SSDI or immediately for ALS. You’ll be notified and mailed your card.
- For ESRD Medicare, contact SSA or your dialysis center for help filing forms to enroll in Medicare Part B (and Part A, if needed)-you may use the CMS-L564 to show proof of any group health plan.
- Seeking Support or Assistance:
- Unsure of your eligibility, form, or best timing? Contact your local State Health Insurance Assistance Program (SHIP) for free help, or visit SSA.gov for guided resources.
Check our guide on How to Cancel Medicare Coverage: Complete Steps if you later need to withdraw or adjust your sign-up.
What Happens After You Sign Up? Coverage Start Dates and Next Steps
After you sign up for Medicare, your coverage start date depends on your enrollment period and eligibility track:
- Turning 65 (IEP): Coverage begins the month you turn 65 (if you apply within the first three IEP months), on your birthday month, or the month after, depending on your sign-up timing. If you sign up after you turn 65, coverage may be retroactive for up to six months, but you may owe back premiums.
- Disability: Medicare Parts A and B automatically start the 25th month after you begin SSDI payments.
- ESRD Medicare: Coverage begins the third month after dialysis starts, or sooner if you start self-dialysis training or get a transplant.
Upon enrollment, you will receive a Welcome to Medicare packet and your red, white, and blue Medicare card. Next steps:
- Create an account at Medicare.gov for personalized plan finder tools, help with billing, and free resources.
- Review your CMS welcome kit for coverage details and deadlines for adding Medigap, Part C, or D.
- Review your premium payment method (direct billing if not on Social Security; deductions if you’re already receiving benefits).
For details on post-enrollment coverage (including skilled nursing), see How Long Will Medicare Pay for Skilled Nursing?
Common Mistakes to Avoid (Late Penalties, Premium Part A)
- Missing Your Initial or Special Enrollment Period: If you do not sign up during your IEP or qualifying SEP, you face a permanent late enrollment penalty for Part B (and for Part A, if not premium-free). The penalty increases the longer you wait and lasts as long as you have coverage.
- Not Applying When Automatic Enrollment Doesn’t Happen: If you are not drawing Social Security/RRB by age 65, you must apply manually-do not wait for a Medicare card to come in the mail.
- Mistakes for ESRD and Workers: Those with ESRD do not qualify for the Working Aged SEP; be sure you enroll during IEP. If you have group coverage, use the right form (CMS-L564) to document employer coverage for a valid SEP.
Be proactive-set reminders and confirm your application status with SSA to avoid coverage gaps and extra costs.
Medicare Parts C and D: Joining Plans After A/B Enrollment
Once you’re enrolled in Medicare Part A and B, you can consider whether you want to join Medicare Part C (Medicare Advantage) or Medicare Part D (prescription drug coverage).
How to Enroll in Part C and D
Parts C and D are offered by private insurers but regulated by Medicare. Use the Annual Enrollment Period (October 15-December 7) or Special Enrollment Periods (after specific life events) to apply. Plan options, including costs and coverage, can be compared at Medicare.gov.
You must have both Parts A and B to enroll in a Medicare Advantage plan. Part D (for prescriptions) can be added independently if you remain on Original Medicare. Some Advantage plans include drug coverage within their integrated offering.
If you’re transitioning from original Medicare to Medicare Advantage, be aware of potential changes in network providers, costs, and coverage options. Use the free plan finder tools and support from SHIP counselors to make the right decision.
For a better understanding of Medicare’s broader organizational structure and oversight, see our article on What Is CMS for Medicare? Key Functions and Role Explained.
