When Can I Enroll in Medicare? Turning 65 Enrollment Periods and Deadlines

When can I enroll in Medicare? For most people, the first chance is a 7-month window around your 65th birthday. It opens 3 months before the month you turn 65, includes your birthday month, and closes 3 months after it.

That is only the first door, though. If you are still working, collecting disability benefits, on dialysis, or you simply missed your window, a different set of dates applies to you, and each one has its own rule for when coverage actually begins.

This guide lays out every sign-up window for Part A and Part B, plus the separate clocks for drug plans, Medicare Advantage and Medigap. Every date comes from Medicare.gov, the Social Security Administration or the federal enrollment rules in 42 CFR Part 407.

Key Takeaways

• Your Initial Enrollment Period lasts 7 months: 3 months before the month you turn 65, that month, and 3 months after. Sign up in the first 3 months and Part B starts the month you turn 65.
• Sign up in your birthday month or later and Part B starts the month after you sign up, so waiting until the last month can leave you uncovered for up to 4 months.
• If you are still covered by a job (yours or your spouse’s), you can wait and use an 8-month Special Enrollment Period after the job or the coverage ends. COBRA and retiree plans do not count.
• Miss every window and you are limited to the General Enrollment Period, January 1 to March 31, with a Part B penalty of 10% for each full year you went without it.
• People on SSDI get Medicare after 24 months of benefits. People with ALS get it when benefits start, and people on dialysis usually start in the fourth month of treatment.

When can I enroll in Medicare for the first time?

You can first enroll during your Initial Enrollment Period, which Medicare.gov describes as 7 months long, “starting 3 months before you turn 65, and ending 3 months after the month you turn 65.” You do not need to be retired, and you do not need to be collecting Social Security to apply.

The federal rule behind this window is 42 CFR 407.14, which defines it as “the 7-month period that begins 3 months before the month an individual first meets the eligibility requirements” and ends 3 months after that month. For people turning 65, the month you meet the requirement is your birthday month.

The window is the same for Part A and Part B. Most people qualify for premium-free Part A because they or a spouse worked about 10 years in jobs that paid Medicare taxes, so Part A costs nothing to add.

Part B has a monthly premium, which is $202.90 in 2026. The 2027 amount had not been announced as of October 22, 2026.

A worked example: turning 65 in March 2027

Say your 65th birthday is March 14, 2027. Your Initial Enrollment Period runs from December 1, 2026 through June 30, 2027. The month you apply decides when your Part B card becomes usable, based on the start-date table on Medicare.gov and the post-2023 rule in 42 CFR 407.25.

You sign up in	Where that falls	Part B starts	Months without Part B after turning 65
December 2026	3 months before	March 1, 2027	0
January 2027	2 months before	March 1, 2027	0
February 2027	1 month before	March 1, 2027	0
March 2027	Birthday month	April 1, 2027	1
April 2027	1 month after	May 1, 2027	2
May 2027	2 months after	June 1, 2027	3
June 2027	3 months after	July 1, 2027	4

The pattern is simple once you see it laid out. Apply before your birthday month and you have no gap at all. Apply on or after it and coverage begins on the first day of the following month, so each month you wait adds one more uncovered month.

Before 2023 the gap could be longer. Under the old rule, signing up in the last months of the window could push your start date back as far as 3 months after you applied.

A rule change for enrollments on or after January 1, 2023 fixed that, and 42 CFR 407.25 now says entitlement begins “with the month following the month in which they enroll.”

What if your birthday is on the first of the month?

Medicare treats you a little differently. Medicare.gov notes that if your birthday falls on the first, your premium-free Part A “starts the month before you turn 65.” Someone born on April 1 would see Part A begin March 1.

Because that shifts your dates by a month, it is worth checking your own window with the Medicare.gov sign-up date tool rather than counting months by hand.

Do you have to sign up, or does Medicare start automatically?

It depends on whether you already get Social Security. Medicare.gov says you are enrolled automatically at 65 “as long as you start getting Social Security benefits at least 4 months before you turn 65.” Everyone else has to apply through Social Security.

If you are enrolled automatically, you get both Part A and Part B, and Medicare mails a welcome package with your card about 3 months before coverage begins. If you do not want Part B yet, Medicare.gov says to follow the package instructions and send the card back. Keep the card and you keep Part B and its premium.

Not sure what the Part A half of that card pays for? Our guide to what Medicare Part A covers walks through hospital, skilled nursing, hospice and home health rules.

Many people now delay Social Security past 65, since full retirement age is 67 for anyone born in 1960 or later. If that is you, nothing happens automatically. You need to apply for Medicare yourself, even though your retirement check is still years away.

There is one regional exception. If you live in Puerto Rico or outside the U.S., Medicare.gov says you “get Part A automatically. If you want Part B, you need to sign up for it.” Miss the 3 months after you turn 65 and you may face the same wait and penalty as anyone else.

How early can you apply for Medicare?

The earliest you can apply is the first day of the third month before your birthday month. For a June birthday, that is March 1. Applying in those first 3 months is the only way to have Part B start the same month you turn 65.

Social Security handles the application, not Medicare. The fastest route is online at SSA.gov, where you can apply for Part A and Part B, or Part A only. You need a my Social Security account to do it.

Have a few items ready: your Social Security number, where you were born, and the start and end dates of any group health plan you have had since 65. Medicare.gov says the welcome package with your card arrives about 2 weeks after you sign up.

If you or your spouse worked for a railroad, you apply through the Railroad Retirement Board instead, at 1-877-772-5772. If you prefer to talk to someone, Social Security takes Medicare applications at 1-800-772-1213 (TTY 1-800-325-0778).

When should you sign up if you are still working past 65?

If you have group health coverage from your current job or your spouse’s current job, you can usually delay Part B. Social Security says you can then sign up “any time while working and still covered by the group health plan,” or within 8 months after the job or the coverage ends.

That second window is the Special Enrollment Period for working people. According to Medicare.gov, it “ends 8 months after the group health plan coverage or the employment ends, whichever happens first.” Sign up inside it and you avoid the late penalty.

Employer size matters. Medicare.gov warns that if the employer has fewer than 20 employees, “your job-based coverage might not pay for health services if you don’t have both Part A and Part B.” Medicare.gov says that with an employer that small, “Medicare pays first,” so most people in that spot sign up at 65.

Even if you delay Part B, it often makes sense to take premium-free Part A at 65, because it costs nothing. The main exception is a Health Savings Account. Medicare.gov says you and your employer should stop HSA contributions 6 months before you retire or apply, because Part A can start up to 6 months back.

To avoid a gap when you retire, Medicare.gov suggests signing up for Part B the month before you or your spouse plan to retire. You will also fill out an extra form showing you had job-based coverage while you or your spouse worked.

If you sign up while still working, you can ask to delay your Part B start by up to 3 months.

When you finally retire, compare your options before choosing between Original Medicare with a supplement and a private plan. Our guide to Medicare Advantage vs Original Medicare walks through the cost and network trade-offs.

Why COBRA and retiree plans do not protect you

This is the rule most worth reading twice. Medicare.gov is direct: “COBRA isn’t considered group health plan coverage,” and “getting COBRA doesn’t change when this Special Enrollment Period ends.” The 8-month clock starts when the job ends, not when COBRA ends.

Retiree coverage works the same way. Medicare.gov lists “your COBRA coverage or retiree coverage ends” among the situations that do not qualify for a Special Enrollment Period. If you sit on COBRA for 18 months, your 8-month window has already closed.

The fix is to sign up for Part B within 8 months of leaving the job, even if you keep COBRA for a while. Ask your former employer’s plan how it coordinates with Medicare before you drop either one.

If you have a Marketplace plan at 65

Marketplace coverage from HealthCare.gov does not give you a Special Enrollment Period later. Medicare.gov lists “you have or lose your Marketplace coverage” as a situation that does not qualify, so treat your 7-month window at 65 as your real deadline.

Once you are eligible for premium-free Part A, you also lose help paying Marketplace premiums. Medicare.gov warns that if you keep getting that help, “you may have to pay back all or part” of it at tax time.

Plan the switch so your Marketplace plan ends when Medicare begins. For Marketplace dates, see our ACA Open Enrollment guide.

VA care, TRICARE and CHAMPVA

VA health care is not job-based coverage, so it does not let you wait. Medicare.gov says you are not eligible to sign up any time “if you can’t get VA services when you need them,” and recommends signing up when first eligible to avoid the Part B penalty.

TRICARE and CHAMPVA go further: you generally need both Part A and Part B to keep that coverage once you qualify for Medicare. Medicare.gov says plainly, “You need to sign up for both Part A and Part B to keep your CHAMPVA coverage.” Our CHAMPVA guide explains how the two work together.

What happens if you missed your Initial Enrollment Period?

If you missed your first window and do not qualify for a Special Enrollment Period, you can sign up during the General Enrollment Period, January 1 to March 31 each year. Coverage starts the first day of the month after you sign up, and you may owe a late penalty.

The start date changed in 2023. Before then, anyone who used the General Enrollment Period waited until July 1 for coverage. Under 42 CFR 407.25, enrollments on or after January 1, 2023 begin “on the first day of the month following the month in which they enroll.” Sign up February 10 and Part B starts March 1.

The penalty is the part that lasts. Medicare.gov says you pay “an extra 10% for each year you could have signed up for Part B, but didn’t,” and you usually pay it for as long as you have Part B. It is added to your premium every month, not charged once.

Medicare.gov gives its own 2026 example. Someone who waited 24 months owes a 20% penalty: $202.90 plus $40.58, or $243.50 a month after rounding. Our Part B premium guide has the full 2026 premium and income brackets.

There is a way around the penalty for people with low income. Medicare.gov says you generally will not pay a Part B penalty if you “enroll in a Medicare Savings Program.” Check our Medicare Savings Programs guide for the income limits.

If you have to buy Part A because you lack 10 years of work, a separate penalty applies. Your Part A premium may rise 10%, and you pay it for twice the number of years you could have signed up but did not. Our Part A premium guide covers who pays for Part A.

Which situations open a Special Enrollment Period?

Beyond working past 65, Medicare offers several “exceptional condition” Special Enrollment Periods created for situations on or after January 1, 2023. Each lets you sign up for Part B or premium Part A outside the normal windows, usually without a late penalty.

Medicare.gov lists these situations and how long each one lasts:

Your situation	How long you have	Coverage starts
You lost Medicaid coverage	Until 6 months after Medicaid ends	Month after you sign up, or the date Medicaid ends
A declared disaster or emergency kept you from signing up	Until 6 months after the declaration ends	Month after you sign up
Your employer or health plan gave you wrong information	6 months from when you tell Social Security	Month after you sign up
You were released from incarceration	Through the 12th month after release	Month after you sign up, or back to release (up to 6 months)
You volunteered abroad with coverage there	6 months	Month after you sign up
You have TRICARE	12 months from when Social Security notifies you	Month after you sign up
Other exceptional conditions Social Security approves	At least 6 months from when you contact SSA	Month after you sign up

For most of these, you fill out form CMS-10797 and send it to your local Social Security office by fax or mail. The “other exceptional conditions” path requires you to contact Social Security first and explain what happened.

Keep notes as you go. If you are claiming that an employer or plan misled you, write down who told you what and when, since Social Security will ask. These periods are not a general second chance, so do not count on one if you simply forgot.

When can you get Medicare before 65?

You can get Medicare before 65 in three cases: after 24 months of Social Security disability benefits, right away if you have ALS and get disability benefits, or with End-Stage Renal Disease. Supplemental Security Income alone does not qualify.

After 24 months of SSDI

Medicare.gov says you are first eligible “after you’ve been getting disability benefits for 24 months,” and you are enrolled in Part A and Part B automatically. Your card arrives about 3 months before coverage starts. CMS notes that your Initial Enrollment Period sits around the 25th month of disability benefits.

The 24 months count from your first month of disability benefit entitlement, which is not always the month your claim was approved.

If you were awarded back pay, ask Social Security for your entitlement date so you know when Medicare will begin. Our SSDI back pay guide explains how those dates are set, and the SSDI program page covers who qualifies.

Social Security is clear that SSI is a different program. Its sign-up page says “Supplemental Security Income (SSI) does not qualify you for Medicare on its own.” Our SSI vs SSDI guide explains the difference.

ALS

People with ALS skip the 24-month wait. Medicare.gov says you are first eligible “as soon as you start getting disability benefits, if you have ALS.” If you already receive those benefits, you should already have Part A and Part B.

End-Stage Renal Disease

Kidney failure follows its own clock, and you have to apply; it is not automatic. Medicare.gov says coverage “usually starts on the first day of the fourth month of your dialysis treatments,” and that the 4-month waiting period starts even if you have not signed up yet.

Two situations start coverage sooner. If you complete home dialysis training, coverage can start the month you begin regular dialysis. For a kidney transplant, coverage can begin the month you are admitted if the transplant happens that month or within the next 2 months.

Medicare.gov adds that if you are eligible because of ESRD and do not sign up right away, coverage “could start up to 12 months before the month you apply.” The working-past-65 Special Enrollment Period does not apply to ESRD, so call Social Security at 1-800-772-1213 and say you are applying because of ESRD.

When can you join a Part D drug plan or Medicare Advantage plan?

Your first chance to join a Part D drug plan or Medicare Advantage plan is the same 7-month Initial Enrollment Period. You need both Part A and Part B for a Medicare Advantage plan, and either Part A or Part B for a stand-alone drug plan.

Timing your plan request matters too. Medicare.gov says that if you ask to join before Part A or Part B starts, plan coverage starts the same day. If you ask after, it starts the first of the month after the plan gets your request.

Skipping drug coverage has its own lifetime penalty. Medicare.gov says you pay “an extra 1% for each month” if you do not join a drug plan when you first get Medicare and go 63 days or more without creditable drug coverage. Job-based, VA or TRICARE drug coverage often counts as creditable.

The penalty is based on the national base beneficiary premium, $38.99 in 2026. Medicare.gov’s example: a 14-month delay adds $5.50 a month for 2026, for as long as you have drug coverage.

Our Part D costs guide explains the 2026 and 2027 cost changes, and if you qualify for Extra Help, Medicare.gov says you generally will not owe this penalty.

If you sign up for Part B later, for example after leaving a job, you get a separate window to pick a plan. Medicare.gov says you have “2 months after you get both Part A and Part B for the first time to join a plan.”

New enrollees also get a short trial period. If you joined a Medicare Advantage plan during your Initial Enrollment Period, you can switch plans or go back to Original Medicare “within the first 3 months you have Medicare Part A and Part B.”

The yearly change windows, briefly

After you are enrolled, two yearly windows let you change plans. Open Enrollment runs October 15 to December 7, with changes starting January 1. If you are already in a Medicare Advantage plan, you also get January 1 to March 31 to switch plans or return to Original Medicare.

Those windows are for changing coverage you already have, not for first-time sign-up. Our Medicare Open Enrollment guide covers the October to December window in detail.

When is the best time to buy a Medigap policy?

The best time is your 6-month Medigap Open Enrollment Period. Medicare.gov says it “starts the first month you have Medicare Part B and you’re 65 or older.” During it, you have the right to buy any Medigap policy sold by an insurance company in your state.

This window happens once in your life. Medicare.gov is explicit that it “doesn’t repeat every year, like the Medicare Open Enrollment Period.” After it closes, an insurer may charge more, offer fewer choices, or deny you if you do not meet its medical underwriting rules.

That is why delaying Part B can be useful if you are still working. Your Medigap window does not start until Part B starts, so people with good employer coverage keep the window intact until they retire and actually need a supplement.

People under 65 on Medicare because of a disability or ESRD face a harder market. Medicare.gov says federal law “generally doesn’t require insurance companies to sell Medigap policies to people under 65,” though insurers in some states do offer them.

To compare plans, see Medigap Plan G vs Plan N and Medicare Advantage vs Medigap.

A month-by-month plan for the year you turn 65

Here is how the rules above fit into a simple schedule. Count backward from your birthday month and adjust if you are still working or born on the first of the month.

1. 6 months before: Check whether your employer has 20 or more employees and whether its plan pays before or after Medicare. If you have an HSA, Medicare & You 2027 says to make your last contribution the month before you turn 65 if you sign up at 65.
2. 4 months before: Decide whether to start Social Security. Starting benefits by now means Medicare enrolls you automatically.
3. 3 months before: Your Initial Enrollment Period opens. Apply at SSA.gov if you are not enrolled automatically and want Part B to start on time.
4. 2 to 1 months before: Compare Medigap, Medicare Advantage and Part D plans so you can request one before Part B begins.
5. Birthday month: Part A starts (or the month before, if you were born on the first). Applying now still works, but Part B begins next month.
6. 3 months after: The last month of your window. After this, you need a Special Enrollment Period or the January to March General Enrollment Period.

Retiring later? Use the same list, but measure from your last day of work or the end of group coverage, whichever comes first, and finish signing up inside the 8 months that follow.

Who can check your dates if your situation is unusual?

Several free sources can confirm your dates. Social Security sets your enrollment periods, so call 1-800-772-1213 for a definite answer about your window. Your State Health Insurance Assistance Program (SHIP) offers free counseling and is not tied to any insurance company.

Bring your birth date, Social Security start date if any, and the dates of every job-based plan you have had since 65. Those three facts answer almost every enrollment question in this guide.

Related reading:

• Medicare program guide: Parts A, B, C and D
• Medicare IRMAA income brackets
• Help paying Medicare costs on a low income
• Medicare vs Medicaid: who qualifies for each