Medicare Enrollment Guide
When Should You Sign Up for Medicare?
Your correct enrollment window depends on age, disability benefits, active employment, employer size, COBRA, retiree insurance and HSA contributions.
If you are not already receiving Social Security benefits and do not have qualifying coverage based on current employment, plan to apply for Medicare about three months before turning 65.
If you or your spouse is actively working and you are covered by that current job’s group health plan, you may be able to delay Part B. Do not delay based solely on COBRA, retiree insurance, VA benefits, Marketplace coverage or an individual policy.
Will Medicare enroll you automatically?
You may be enrolled automatically
If you begin receiving Social Security or Railroad Retirement benefits at least four months before turning 65, you are generally enrolled automatically in Medicare Parts A and B.
You should receive a Medicare welcome package and card about three months before coverage begins. Review it promptly, especially if you plan to delay Part B because of current-employment coverage.
You may need to apply
If you are not receiving Social Security or Railroad Retirement benefits before 65, Medicare enrollment is generally not automatic. Apply through Social Security even if you are delaying retirement benefits.
Medicare eligibility and the age at which you claim Social Security retirement benefits are separate decisions.
People living in Puerto Rico or outside the United States can face different automatic Part B enrollment procedures. Review the welcome package or contact Social Security rather than assuming Part B is active.
Your first Medicare enrollment window usually lasts seven months
For most people becoming eligible at 65, the Initial Enrollment Period begins three months before the birthday month, includes the birthday month and ends three months afterward.
Apply before your birthday month
If you enroll in Part B or premium-Part A during the first three months of the Initial Enrollment Period, coverage generally begins the first day of the month you turn 65.
Apply during or after your birthday month
If you enroll during your birthday month or one of the three following months, Part B and premium-Part A generally begin the first day of the month after enrollment.
Birthday on the first day of the month?
Your Medicare age-65 timeline generally shifts one month earlier. For example, someone born August 1 is treated as reaching Medicare age in July. Premium-free Part A and timely Part B coverage generally begin July 1.
Can you delay Medicare because you have employer coverage?
Sometimes—but the coverage generally must be tied to your or your spouse’s current employment.
Confirm that the coverage is based on current employment
Ask the employer whether the insurance is an employer group health plan based on active work. Retiree coverage and COBRA are not treated the same way.
Ask which coverage pays first
The employer’s size and your reason for Medicare eligibility affect whether Medicare or the employer plan is primary. If Medicare should be primary and you fail to enroll, the employer plan may pay as though Medicare had already paid.
Compare the employer plan with Medicare
Consider premiums, deductibles, provider access, prescription coverage, dependent coverage and HSA contributions. Having permission to delay Part B does not automatically mean delaying is the least expensive choice.
Plan the Part B start before employment coverage ends
Apply in advance when possible so Part B begins as the job-based coverage ends. Waiting until afterward can create a healthcare gap.
Small- and large-employer coverage may coordinate differently
| Situation | General coordination rule | What to investigate |
|---|---|---|
| Age 65+ with employer of 20 or more employees | The active employer plan generally pays first and Medicare pays second. | Delaying Part B may be possible, but verify that the plan qualifies and compare costs. |
| Age 65+ with employer under 20 employees | Medicare generally pays first and the employer plan pays second. | You may need Parts A and B at 65 even while actively working. Confirm directly with the employer and insurer. |
| Under 65 due to disability | Coordination commonly depends on whether the employer has 100 or more employees. | Ask the employer, insurer and Medicare which coverage is primary. |
| Medicare due to ESRD | Separate coordination-period rules apply. | Do not rely only on the ordinary age-65 employee thresholds. |
Employer ownership, affiliated companies and multi-employer arrangements can affect how employee counts are determined. Obtain the answer from the benefits administrator and health plan in writing when possible.
Do not assume other insurance lets you delay Part B
COBRA
COBRA is not coverage based on current employment. Electing COBRA does not stop or restart the eight-month Part B Special Enrollment Period.
Retiree coverage
Retiree insurance generally does not preserve the current-employment Part B enrollment right. It may also require Medicare Parts A and B to pay correctly.
Marketplace coverage
Individual Marketplace insurance does not normally protect you from the Part B late-enrollment penalty or create the current-employment SEP.
VA benefits
VA coverage can be valuable but generally does not replace Medicare enrollment or create a Part B Special Enrollment Period. Medicare and VA typically pay under separate systems.
TRICARE
Many people must have Medicare Parts A and B to retain TRICARE For Life. Active-duty families and people with ESRD can face different rules.
Medicaid
Medicaid does not make Medicare enrollment unnecessary. A state may help enroll eligible beneficiaries or pay Medicare premiums through a Medicare Savings Program.
The COBRA deadline trap
The eight-month Part B SEP begins when active employment or its job-based coverage ends, whichever happens first. If you elect 18 months of COBRA and wait until COBRA ends, the Part B SEP may already be over.
Medicare enrollment and HSA contributions require advance planning
You cannot contribute to an HSA after Medicare coverage begins
You may continue spending existing HSA funds on qualified expenses, but neither you nor your employer may make HSA contributions for months in which you are enrolled in any part of Medicare.
When someone enrolls in premium-free Part A after age 65, Part A may begin retroactively for as many as six months—but not before the first month of Medicare eligibility. This can turn recent HSA contributions into excess contributions.
If enrolling at age 65
Medicare’s current guidance generally calls for stopping HSA contributions before the month Medicare begins. A first-of-the-month birthday can move Medicare eligibility one month earlier.
If enrolling more than six months after 65
Medicare advises stopping HSA contributions at least six months before applying for Medicare, Social Security or Railroad Retirement benefits because premium-free Part A may be retroactive.
HSA rules are tax rules as well as Medicare rules. Coordinate the enrollment date with the employer’s benefits department and a qualified tax professional.
Signing up after current-employment coverage ends
While still working and covered
If you qualify, you can generally enroll in Part B while the current-employment group health coverage is still active.
After the job or coverage ends
The Part B Special Enrollment Period generally lasts eight months after the employment or qualifying group coverage ends, whichever happens first.
Do not confuse the eight-month Part B enrollment window with the shorter windows for joining a Medicare Advantage plan, Part D plan or obtaining certain Medigap protections. Waiting eight months can still create other coverage problems.
Exceptional-circumstance enrollment periods
Since 2023, additional Special Enrollment Periods can help certain people who missed Medicare enrollment for specified reasons.
Losing Medicaid
A limited SEP may apply when someone loses Medicaid after missing Medicare enrollment. The notice and Medicaid termination dates affect the available period.
Disaster or emergency
Relief may apply when a federal, state or local emergency prevented you, your representative, guardian or caregiver from completing enrollment.
Incorrect information
A SEP may apply when material misinformation from an employer or health plan caused the missed enrollment.
Release from incarceration
People released from incarceration may have a SEP ending on the last day of the twelfth month after the month of release. Retroactive coverage options may be available.
Termination of Medicaid coverage
Medicare plan enrollment options may also be available when Medicaid coverage ends, even when Parts A and B are already active.
Other exceptional conditions
Social Security can evaluate other exceptional circumstances under Medicare rules. Approval and timing depend on the individual facts.
Social Security—not an insurance broker—determines eligibility for Medicare Parts A and B and these exceptional enrollment periods.
What if you missed your other enrollment opportunities?
January 1 through March 31
The General Enrollment Period is available each year for people who missed their Initial Enrollment Period and do not qualify for another Part A or Part B enrollment opportunity.
Coverage begins the following month
Under current rules, Part B and premium-Part A coverage generally begin the first day of the month after enrollment during the General Enrollment Period.
Using the General Enrollment Period can involve penalties
A General Enrollment Period application does not erase a late-enrollment penalty. Social Security calculates whether a penalty applies based on prior eligibility and coverage.
Already enrolled in Medicare and noticing that your coverage feels different after the new year? That is a separate issue from the General Enrollment Period. Read the Medicare mistake to avoid every January .
How delayed enrollment can affect Medicare costs
Premium-Part A penalty
If you must buy Part A and delay without a protected enrollment right, the premium may increase by 10%. The higher premium generally applies for twice the number of years enrollment was delayed.
Part B penalty
The Part B premium generally increases by 10% for each full 12-month period you could have had Part B but did not. It normally continues for as long as you have Part B.
Part D penalty
A penalty may apply after 63 continuous days without Part D or other creditable drug coverage. The calculation uses 1% of the national base beneficiary premium for each full uncovered month.
Part D’s national base beneficiary premium can change annually, so the monthly penalty may change even when the number of uncovered months stays the same. People who qualify for Extra Help do not pay the Part D late enrollment penalty.
Disability, ALS and ESRD follow different timelines
Social Security disability
Most people receiving qualifying disability benefits are automatically enrolled in Parts A and B after 24 months of disability-benefit entitlement.
ALS
People with amyotrophic lateral sclerosis generally receive Medicare when qualifying disability benefits begin, without the ordinary 24-month Medicare waiting period.
End-Stage Renal Disease
ESRD eligibility and effective dates depend on dialysis, transplant and training circumstances. Enrollment may not be automatic, so contact Social Security promptly.
Turning 65 while already enrolled in Medicare because of disability generally does not require signing up for Parts A and B again. However, age 65 can create new Medigap rights and plan-comparison opportunities.
Social Security handles Medicare Parts A and B enrollment
Railroad Retirement Board
If you or your spouse worked for a railroad, Medicare enrollment may be handled through the Railroad Retirement Board.
Phone: 1-877-772-5772
Thompson Medicare can help you identify the likely enrollment window, organize questions and understand the insurance choices that follow. Social Security or the Railroad Retirement Board makes the official Parts A and B eligibility and enrollment decision.
Original Medicare enrollment is only the first decision
Medicare Advantage
You generally need both Part A and Part B to join a Medicare Advantage plan and must live in the plan’s service area.
Learn about Medicare Advantage →Medicare Supplement
Your federal Medigap Open Enrollment Period generally lasts six months beginning when you are both 65 or older and enrolled in Part B.
Learn about Medicare Supplements →Prescription drug coverage
You can generally join a Part D plan with Part A or Part B. Avoid going 63 days without Medicare drug coverage or other creditable coverage.
Learn about Medicare Part D →Do not assume Part A and Part B cover everything
Original Medicare does not include most outpatient prescription drugs and has no annual out-of-pocket maximum. Most beneficiaries evaluate Medicare Advantage or pair Original Medicare with Part D and, when eligible, Medigap or other supplemental coverage.
Questions to answer before delaying Medicare
- Am I already receiving Social Security or RRB benefits?
- Is my coverage based on current employment?
- Is the active employee me, my spouse or another family member?
- How many employees does the employer have?
- Which coverage pays first after I become Medicare eligible?
- Does the employer plan require Medicare enrollment?
- Am I or my employer contributing to an HSA?
- Is the drug coverage officially creditable?
- Will dependents lose coverage if I leave the employer plan?
- When does employment or coverage actually end?
- Do I have COBRA, retiree, VA or TRICARE coverage?
- When should my new Medicare coverage begin?
Medicare enrollment FAQ
Do I automatically get Medicare when I turn 65?
Usually only if you began receiving Social Security or Railroad Retirement benefits early enough before turning 65. Otherwise, you generally need to apply through Social Security.
Do I need to start Social Security to get Medicare?
No. You can apply for Medicare without starting monthly Social Security retirement benefits.
Should I sign up exactly on my 65th birthday?
Usually not. If you need Medicare at 65, applying during the three months before your birthday month provides more time for processing and generally allows coverage to begin when first eligible.
Can I delay Part B if I am still working?
Possibly, if you have qualifying group health coverage based on your or your spouse’s current employment. Employer size and which plan pays first must also be checked.
Can I delay Part B because I have COBRA?
COBRA does not count as coverage based on current employment. Your eight-month Part B SEP generally begins when active employment or its group coverage ends, even if you elect COBRA.
Can I delay Medicare because I have VA benefits?
VA benefits do not generally create a Part B Special Enrollment Period. Medicare and VA coverage can work alongside each other, but they usually pay through separate healthcare systems.
Should I take premium-free Part A while working?
It can make sense for some people, but not if you want to continue contributing to an HSA. Also check how Part A coordinates with the employer plan before enrolling.
Can I keep contributing to my HSA after enrolling in Part A?
No. HSA contributions are not permitted for months in which you are enrolled in Medicare. Retroactive Part A can make this especially complicated for people enrolling after age 65.
What forms are commonly used when retiring after 65?
A person applying for Part B after current-employment coverage commonly uses Form CMS-40B, while the employer documents prior coverage through Form CMS-L564. Social Security determines which documents are required.
Do I sign up for Medicare Advantage through Social Security?
No. Social Security handles Parts A and B. After those effective dates are established, you can enroll in an eligible private Medicare Advantage or Part D plan through Medicare, the plan or an authorized agent or broker.
Do I sign up again at 65 if I already have Medicare through disability?
Generally, no. Parts A and B continue. However, turning 65 can create new Medigap rights and is a good time to review all coverage options.
Can a Medicare broker guarantee that Social Security will approve my SEP?
No. A broker can help identify the likely rule and explain the insurance decisions, but Social Security makes the official eligibility, effective-date and penalty determination.
Related Medicare guides
Make the Medicare decision before a deadline makes it for you
Benjamin Thompson can help you identify the questions to ask your employer, understand how your existing coverage coordinates and prepare for the Medicare Advantage, Medigap and Part D decisions that follow Parts A and B enrollment.
Missouri: (417) 420-1807 | Illinois: (217) 661-2332