Medicare is a federal health insurance program in the United States for individuals aged 65 and older, younger people with disabilities, and people with End-Stage Renal Disease (ESRD). Navigating the different parts of Medicare can be confusing, especially when trying to understand the basics of Medicare Part A and Part B. This guide will clarify what Medicare Part A and Part B cover, who is eligible, and how to enroll, ensuring you have a solid understanding of these foundational components of Medicare.
Understanding Medicare Part A (Hospital Insurance)
Medicare Part A, often referred to as Hospital Insurance, helps cover your costs when you are a hospital inpatient. For most people, Part A is premium-free, meaning you don’t have to pay a monthly premium.
Eligibility for Premium-Free Medicare Part A
To qualify for premium-free Part A, you generally need to have worked and paid Medicare taxes for a certain amount of time. Specifically, you must:
- Be eligible to receive Medicare based on your work history or that of your spouse, parent, or child.
- Have accumulated a specific number of quarters of coverage (QCs) through paying payroll taxes under the Federal Insurance Contributions Act (FICA) during your working years. The number of QCs required depends on whether you are applying based on age, disability, or ESRD.
- File an application for Social Security or Railroad Retirement Board (RRB) benefits.
Most workers who pay full FICA taxes earn QCs that count towards both Social Security benefits and premium-free Part A.
Important Note: Some government employees only pay the Part A portion of FICA taxes. Their QCs only count towards premium-free Part A eligibility and not monthly Social Security benefits.
Premium-Free Part A Based on Age
For age-based eligibility, you must meet these criteria:
- Be 65 years of age or older.
- Be eligible for monthly Social Security or Railroad Retirement Board (RRB) cash benefits.
If you are already receiving Social Security or RRB benefits at least 4 months before turning 65, you will be automatically enrolled in premium-free Part A. You don’t need to file a separate application. Medicare Part A coverage will start automatically when you turn 65.
If you are not receiving Social Security or RRB benefits, you need to apply for Medicare by contacting the Social Security Administration.
Part A coverage typically begins the month you turn 65, as long as you apply within 6 months of your 65th birthday. If you apply later than 6 months after turning 65, your Part A coverage can be retroactive for up to 6 months.
Special Note: If your 65th birthday is on the first day of a month, your Part A coverage starts on the first day of the month before your birth month. For example, if your birthday is December 1st, Part A coverage begins on November 1st.
Premium-Based Medicare Part A
If you don’t qualify for premium-free Part A, you may still be able to get Part A by paying a monthly premium. To enroll in premium Part A, you must:
- Apply for enrollment through the Social Security Administration.
- Enroll during a valid enrollment period.
- Be enrolled in Medicare Part B or already have Part B.
To maintain your premium Part A coverage, you must continue to pay your monthly premiums for both Part A and Part B.
Premium Part A coverage begins the month after you enroll.
Medicare Part A Based on Disability
If you are entitled to Social Security or Railroad Retirement Board (RRB) disability benefits, you are generally automatically entitled to Part A after receiving disability benefits for 24 months. Disabled federal, state, and local government employees who don’t qualify for Social Security or RRB benefits may be deemed entitled and automatically enrolled in Part A after being disabled for 29 months.
Special Rule for ALS (Lou Gehrig’s Disease)
For individuals with Amyotrophic Lateral Sclerosis (ALS), there’s no waiting period. They become entitled to Part A in the first month they are approved for Social Security or RRB disability cash benefits.
Special Rule for Child Disability Benefits
Child disability benefits from Social Security Administration (SSA) cannot begin before age 18. Therefore, Part A entitlement based on child disability benefits cannot start before the month the person turns 20 (or 18 if the disability is ALS).
Medicare Part A Based on End-Stage Renal Disease (ESRD)
Individuals with End-Stage Renal Disease (ESRD) are eligible for premium-free Part A if they:
- Require regular dialysis treatments or need a kidney transplant.
- Have applied for Medicare.
- Meet one of the following work history conditions:
- Have worked enough years under Social Security, the Railroad Retirement Board (RRB), or as a government employee.
- Are currently receiving or are eligible for Social Security or RRB benefits.
- Are the spouse or dependent child of someone who meets the work history requirements or is receiving Social Security or RRB benefits.
Part A coverage start dates for ESRD depend on the situation:
- Dialysis: Coverage usually begins the 3rd month after a regular course of dialysis starts.
- Self-Dialysis Training: Coverage can start the first month of regular dialysis if you participate in self-dialysis training.
- Kidney Transplant: Coverage begins the month of the transplant.
- Pre-Transplant Hospitalization: Coverage may start two months before the transplant month if you were hospitalized during those months in preparation for the transplant.
Understanding Medicare Part B (Medical Insurance)
Medicare Part B, known as Medical Insurance, helps cover a range of medical services and supplies, including doctor visits, outpatient care, preventive services, and home healthcare. Part B typically requires a monthly premium.
Individuals already receiving Social Security or RRB benefits at least 4 months before Medicare eligibility and residing in the United States (excluding Puerto Rico residents) are automatically enrolled in both premium-free Part A and Part B. However, you can choose to refuse Part B coverage if desired. Residents of Puerto Rico are automatically enrolled only in Part A and must actively enroll in Part B if they want it.
If you are not receiving Social Security or RRB benefits, you will not be automatically enrolled in Part B. If you previously declined Part B or ended your Part B enrollment, you can only enroll or re-enroll during specific enrollment periods. In most cases, if you don’t enroll in Part B when you are first eligible, you may have to pay a late enrollment penalty for as long as you have Part B.
Part B is voluntary and requires payment of a monthly premium. Eligibility for Part B depends on whether you are eligible for premium-free Part A or if you must pay a premium for Part A.
If you are eligible for premium-free Part A, you are also eligible to enroll in Part B once you are entitled to Part A.
If you must pay a premium for Part A, you need to meet these requirements to enroll in Part B:
- Be age 65 or older.
- Be a U.S. resident.
- Be a U.S. citizen, OR be an alien lawfully admitted for permanent residence and have lived in the United States for 5 continuous years before applying for Medicare.
Special Note: Individuals who had Part A terminated 36 months after a kidney transplant may be eligible for the Part B Immunosuppressive Drug benefit.
Medicare Enrollment Periods and Coverage Start Dates
If you are eligible for premium-free Part A and are not automatically enrolled, you can enroll in Part A at any time after you become eligible.
For premium Part A, Part B, or both, you can only enroll during specific enrollment periods defined by law. These periods include:
- Initial Enrollment Period (IEP)
- General Enrollment Period (GEP)
- Special Enrollment Period (SEP)
Initial Enrollment Period (IEP)
The Initial Enrollment Period (IEP) is a 7-month window surrounding your 65th birthday. It starts 3 months before the month you turn 65, includes your birthday month, and ends 3 months after your birthday month.
For those under 65 who become eligible for Medicare due to disability, the IEP is linked to the 25th month of disability benefit entitlement. It begins 3 months before the 25th month, includes the 25th month, and ends 3 months after. IEP rules for ESRD and ALS vary depending on individual circumstances.
Coverage will begin the month after you enroll during your IEP. Individuals receiving disability benefits are usually automatically enrolled in Medicare Part A and Part B after 24 months of disability benefits from Social Security.
Important Note: Failing to enroll in Part B or premium Part A during your IEP may result in a late enrollment penalty. The Part B penalty can last as long as you have Part B coverage.
General Enrollment Period (GEP)
The General Enrollment Period (GEP) occurs every year from January 1st to March 31st. If you enroll during the GEP, your Part B and premium Part A coverage will begin the month after you enroll.
Special Enrollment Period (SEP)
Under certain circumstances, you may qualify for a Special Enrollment Period (SEP) to sign up for Part B (and premium Part A) without incurring a late enrollment penalty. SEPs are available for a limited time. If you miss your SEP, you will have to wait for the next General Enrollment Period and may face a late enrollment penalty.
Coverage will begin the month after you enroll during a SEP.
SEP for the Working Aged and Working Disabled
If you didn’t enroll in Part B or premium Part A initially because you had group health plan coverage through your own or a spouse’s current employment (or a family member’s current employment if disabled), you can enroll during this SEP.
You can enroll at any time while you have coverage from the group health plan based on current employment, or within 8 months after the employment ends or the group health plan coverage ends – whichever comes first.
Important Note: This SEP is not available for individuals with ESRD.
SEP for International Volunteers
If you did not enroll in Part B or premium Part A when first eligible because you were volunteering outside the U.S. for at least 12 months with a tax-exempt organization and had health insurance coverage during your service, you may use this SEP.
This SEP is a 6-month period starting from the earlier of:
- The first day of the month after your volunteer service outside the U.S. ended.
- The month after the organization’s tax-exempt status ended.
- The month after your health insurance coverage outside the U.S. ended.
SEP for Certain TRICARE Beneficiaries
Individuals who enroll in Part A due to disability or ESRD, but did not enroll in Part B because they were eligible for TRICARE Standard or TRICARE Prime, can use this SEP.
Eligible individuals are:
- Under age 65, and
- Eligible for TRICARE Standard when they became entitled to Part A, and
- A military retiree or family member of a military retiree, or
- On active duty or a family member of an active-duty service member with Medicare due to ESRD.
Enrollment Timing:
- Notified of Medicare entitlement during IEP: You can enroll the month after your IEP ends.
- Notified of Medicare entitlement after IEP: You can enroll in the month you receive notification.
Coverage Start Dates:
- Notified during IEP: Coverage starts either the month of enrollment or the month after the IEP ends.
- Notified after IEP: Coverage starts either the month of enrollment or the month Part B was terminated (if previously refused).
- Entitlement based on ESRD: Coverage starts the month of Part A entitlement, the month of enrollment, or the month after the IEP ends.
Special Enrollment Period for Exceptional Conditions
Effective January 1, 2023, SEPs are available for exceptional conditions for premium Part A and Part B.
SEP for Individuals Impacted by an Emergency or Disaster
If you missed enrolling in Part B or premium Part A when first eligible due to an emergency or disaster declared by a government entity in your area, you can use this SEP.
You can enroll as early as the month the emergency or disaster began, or up to six months after it ends. This SEP can also apply if the disaster or emergency occurred where your authorized representative, legal guardian, or healthcare decision-maker resides.
The SEP begins on the date the emergency or disaster is declared (or the start date in the declaration, if earlier) and ends six months after the later of:
- The end date of the disaster or emergency declaration.
- The end date of any extensions or the date the declaration is determined to have ended or been revoked.
- The date of the declaration if it is after the disaster’s end.
Medicare benefits will be effective the first day of the month following enrollment.
SEP for Health Plan or Employer Misrepresentation
If you didn’t enroll in Part B or premium Part A when first eligible due to misinformation or incorrect advice from your employer, group health plan, or their agents, you can use this SEP.
To qualify, you must show (through documentation or written statement) that:
- You did not enroll in Part B or premium Part A during an eligible enrollment period based on information from your employer, group health plan, or their representatives.
- Your employer, group health plan, or their representative misrepresented or provided incorrect information about Medicare enrollment.
This SEP starts when you notify the Social Security Administration and lasts for six months. Medicare benefits begin the first day of the month after enrollment.
SEP for Formerly Incarcerated Individuals
If you did not enroll in Part B or premium Part A because you were incarcerated, you can use this SEP.
You can sign up anytime within the first 12 months after your release from incarceration.
- The SEP begins on the day of your release from custody and ends on the last day of the 12th month after release.
- You can choose a retroactive coverage start date (up to 6 months prior, but not before your release date). If you choose retroactive coverage, you will need to pay premiums back to the coverage start date.
Medicare benefits will be effective the first day of the month following enrollment, or retroactively if selected.
SEP to Coordinate with Termination of Medicaid Coverage
If your Medicaid eligibility was terminated, you may use this SEP.
You may be eligible if you lost Medicaid entirely, missed a Medicare enrollment period, and your Medicaid coverage ended on or after January 1, 2023.
- The SEP begins when you are notified of upcoming Medicaid termination and ends six months after Medicaid ends.
- Medicare benefits start the month after enrollment, unless you choose a start date back to the first day of the month Medicaid ended (and agree to pay prior premiums).
Important Note: This SEP is not for individuals still eligible for Medicaid (including Medicare Savings Programs) who haven’t received a Medicaid termination notice.
SEP for Other Exceptional Conditions
If conditions beyond your control caused you to miss a Medicare enrollment period, you can use this SEP. This is for unique situations not covered by other SEPs. You must demonstrate (with documentation or written statement) that conditions outside your control occurring on or after January 1, 2023, caused you to miss enrollment.
This SEP is for truly exceptional cases, not for forgetfulness, lack of knowledge, or failure to pay premiums.
The Social Security Administration will determine the SEP start date on a case-by-case basis, but it will last at least 6 months. Medicare benefits begin the first day of the month after enrollment.
Part A and B Enrollment Forms
To enroll in Medicare Part A and Part B, you may need to complete specific forms. You can download these forms or contact Social Security for assistance.
- CMS-18-F-5: For individuals without Part A who wish to enroll (also used to enroll in Part B simultaneously). For SEP for Working Aged/Disabled, also use CMS-L564.
- CMS-40B: For individuals with Part A but not Part B, to enroll in Part B. For SEP for Working Aged/Disabled, also use CMS-L564.
- CMS-4040: For individuals NOT entitled to Social Security or RRB benefits, to enroll in Part B.
- CMS-43: For individuals with ESRD, to enroll in Part A and Part B.
- CMS-10797: For individuals qualifying for SEP due to exceptional conditions, to enroll in premium Part A and Part B.
- CMS-L564: For SEP for Working Aged/Disabled, to be used with other enrollment forms.
Termination of Enrollment
Premium-free Part A: You generally cannot voluntarily terminate premium-free Part A. It typically ends due to:
- Loss of entitlement to Social Security or Railroad Retirement Board benefits.
- Death.
- Special rules apply for those with ESRD.
Premium Part A and Part B: You can voluntarily terminate premium Part A and Part B because they require premium payments. Coverage ends due to:
- Voluntary disenrollment request.
- Failure to pay premiums.
- For those under 65 (disabled/ESRD), loss of Part A entitlement (Part B terminates too).
- Death.
To disenroll from Premium Part A and Part B, use form CMS-1763.
Premiums, IRMAA, and Late Enrollment Penalties
Premium Part A and Part B coverage require monthly premium payments.
IRMAA (Income-Related Monthly Adjustment Amount)
Higher-income individuals and married couples pay higher premiums for Part B and an extra amount for Part D coverage. This is called the Income-Related Monthly Adjustment Amount (IRMAA). It affects less than 5% of Medicare beneficiaries.
Late Enrollment Penalty (LEP) for Premium Part A
If you don’t enroll in premium Part A when first eligible, you may face a higher monthly premium if you enroll later. The Part A premium can increase by up to 10%. You’ll pay this higher premium for twice the number of years you could have had Part A but didn’t.
For the SEP for Working Aged/Disabled, the LEP is calculated based on months between your IEP closing and the month you enroll, excluding months with group health plan coverage.
No LEP applies for SEPs for Exceptional Conditions or International Volunteers.
Late Enrollment Penalty (LEP) for Part B
If you don’t enroll in Part B when first eligible, you may have to pay a late enrollment penalty for as long as you have Medicare. Your monthly Part B premium may increase by 10% for each full 12-month period you could have had Part B but didn’t sign up.
For the SEP for Working Aged/Disabled, the Part B LEP calculation is similar to Part A, excluding months with group health plan coverage after your IEP.
No LEP applies for SEPs for Exceptional Conditions, International Volunteers, or Certain TRICARE Beneficiaries.
This information is intended to provide a comprehensive overview of Medicare Part A and Part B. For personalized advice and to ensure you understand your specific situation, please contact the Social Security Administration or visit the official Medicare website.
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