General and Special Enrollment Periods: Signing Up Later

Not everyone signs up for Medicare Part B the moment they turn 65. Some people are still working with good employer coverage, some miss the window by mistake, and some are thrown off course by events they couldn't control, like a disaster or wrong information from an employer.

Medicare has two main paths for signing up after your first window closes: the General Enrollment Period, which is open to anyone, and Special Enrollment Periods, which depend on your circumstances. Which one you use can decide whether you pay a late enrollment penalty and how long you wait for coverage. This guide covers signing up for Part A and Part B; changing health and drug plans has its own windows, covered in our guide to fall Open Enrollment.

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The General Enrollment Period

Medicare.gov's 2026 guidance describes the General Enrollment Period as January 1 through March 31 each year. It is the fallback if you missed your Initial Enrollment Period and don't qualify for a Special Enrollment Period. According to the Medicare & You 2027 handbook, you can sign up for Part B then, and you can also buy Part A if you don't qualify for premium-free Part A.

Medicare.gov (2026) says coverage starts the month after you sign up during this period. Even so, if you realize your mistake in the spring or summer, you may go months without coverage while you wait for January.

The bigger cost is the penalty. Medicare.gov's 2026 penalty page says the Part B penalty is an extra 10% for each full 12-month period you could have had Part B but didn't, and that it is usually charged for as long as you have Part B. A separate penalty can apply if you have to buy Part A and delay it. Our Costs & Help Paying section covers penalties in detail.

One more piece: signing up for Part B late also affects when you can join a private plan. Medicare.gov's 2026 joining-a-plan page says that if you already have Part A and add Part B later, you have 2 months after you first have both parts to join a plan, and the 2027 handbook says people who sign up for Part B during the General Enrollment Period have 2 months after signing up to join a Medicare drug plan.

The Special Enrollment Period for job-based coverage

The most widely used Special Enrollment Period is for people who delayed Part B because they had group health coverage based on current employment: their own, a spouse's, or (for people with a disability) a family member's.

Medicare.gov's 2026 rules for this window are:

• It starts the first month after your Initial Enrollment Period ends (Medicare.gov, 2026).
• It ends 8 months after the group coverage or the employment ends, whichever happens first (Medicare.gov, 2026).
• You can sign up any time while you still have the group coverage, according to the Medicare & You 2027 handbook.
• Coverage generally starts the month after you sign up. Medicare.gov (2026) says that if you sign up while still working, or within the first full month after employer coverage ends, you can ask to delay your Part B start date by up to 3 months.

Medicare.gov (2026) adds that this window does not apply if your Medicare eligibility is based on End-Stage Renal Disease, or if you are still in your Initial Enrollment Period. For people under 65 with a disability whose coverage comes from a non-spouse family member's job, it says the employer must have a large group health plan.

When you apply, Medicare.gov (2026) says you'll need an extra form showing you had job-based coverage while you or your spouse were working. Ask your employer for help completing it well before your coverage ends.

Situations that don't qualify

Medicare.gov's 2026 list of situations that do not open a Special Enrollment Period is short and important:

• Your COBRA coverage or retiree coverage ends.
• You missed your 8-month window after you stopped working or lost job-based coverage (Medicare.gov, 2026).
• You have or lose Marketplace coverage.
• You have End-Stage Renal Disease (it has its own rules).

COBRA trips up many people. Medicare.gov (2026) says the employment-based window starts when you stop working even if you choose COBRA, and that getting COBRA doesn't change when the window ends. If you take COBRA after retiring, keep track of the date your job ended, not the date COBRA will end.

Special Enrollment Periods for exceptional situations

Medicare also offers Special Enrollment Periods for situations outside your control. Medicare.gov's 2026 page lists these, each for events on or after January 1, 2023:

• Lost Medicaid: the window opens when you're notified Medicaid is ending and closes 6 months after it ends (Medicare.gov, 2026).
• Natural disaster or declared emergency that kept you, or a representative or caregiver, from signing up: the window closes 6 months after the declaration's end date, extensions or end announcement, whichever is latest (Medicare.gov, 2026).
• Wrong or misleading information from your health plan or employer: the window lasts 6 months from when you notify Social Security (Medicare.gov, 2026).
• Release from incarceration: the window runs through the last day of the 12th month after the month you're released (Medicare.gov, 2026).
• Other exceptional conditions: Medicare.gov (2026) says you must contact Social Security to ask, and the window lasts at least 6 months from then.

For these situations, Medicare.gov (2026) points you to form CMS-10797, sent to your local Social Security office by fax or mail. Medicare.gov's 2026 joining-a-plan page adds that if you sign up through one of these exceptional-situation windows, you'll have 2 months to join a Medicare Advantage Plan or drug plan.

Two more Special Enrollment Periods are worth knowing. Medicare.gov (2026) describes one for people volunteering in a foreign country with a tax-exempt organization, lasting 6 months after the volunteer work or related coverage ends, and one for people with TRICARE, lasting 12 months from when Social Security notifies you.

A hypothetical example

Imagine Dana, 67, who kept Part A at 65 but delayed Part B because her employer's group plan covered her. She retires at the end of June and elects COBRA through December. Under the rules Medicare.gov described in 2026, her 8-month Special Enrollment Period runs from her retirement, not from the end of COBRA. If she waited until COBRA ended in December, she would have only a couple of months left, and if she missed the window entirely she would be looking at the General Enrollment Period and a possible penalty. Signing up for Part B in June, with her employer's form, avoids both risks.

How to protect yourself

• Keep proof of coverage: letters, notices and dates showing when your employer coverage or employment ended.
• Write down the end date of your Special Enrollment Period the day your job or coverage ends.
• Be wary of anyone who calls offering to sign you up. The Medicare & You 2027 handbook says not to share your Medicare Number with anyone who contacts you by phone, email or in person unless you've given them permission in advance.
• Get help early. Your State Health Insurance Assistance Program (SHIP) offers free counseling, and Social Security handles Part A and Part B enrollment and the exceptional-situation requests.

Key takeaways

• Medicare.gov (2026) lists the General Enrollment Period as January 1 to March 31 each year, with coverage starting the month after you sign up and a possible late penalty.
• Active job-based coverage opens a Special Enrollment Period that, per Medicare.gov (2026), ends 8 months after the job or coverage ends, whichever comes first.
• COBRA, retiree coverage, Marketplace coverage and missed deadlines don't open a Special Enrollment Period.
• Exceptional-situation windows exist for lost Medicaid, disasters, employer or plan errors and incarceration, requested through Social Security.
• Keep documents showing when your coverage ended; you may need them to prove you qualify.

Sources

• Medicare.gov (CMS), When does Medicare coverage start?
• Medicare.gov (CMS), When can I sign up for Medicare?
• Medicare.gov (CMS), Avoid late enrollment penalties
• Medicare.gov (CMS), Working past 65
• Centers for Medicare & Medicaid Services, Medicare & You 2027 (official handbook)
• Medicare.gov (CMS), Contact Medicare and get help
• Medicare.gov (CMS), Joining a plan