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What Are Medicare’s 3 Enrollment Periods?

You can’t apply whenever you want. Learn the distinct times you’re allowed to sign up

7-minute read

Article 6 out of 15 in Medicare Basics

Kimberly Lankford,

Updated August 07, 2026

AARP

Reviewed by

Xavier Vaughn, MPH

En español

Updated August 07, 2026

Illustration of a hand flipping the page of a desk calendar that resembles a red, white and blue Medicare card.

Rob Dobi

Key takeaways

Medicare won’t let you sign up whenever you want.
If you get Social Security, enrollment may be automatic.
Initial enrollment centers around your 65th birthday.
Working past 65 may qualify you for special enrollment.
Miss your other chances? General enrollment is your option.

If you’re used to streaming entertainment on demand, shopping at 2 a.m. and getting restaurant delivery with a few taps, Medicare may feel a little retro.

Think of it like 1990s appointment TV: You can’t sign up whenever you want. Medicare’s three enrollment periods — initial, special and general — set the times you can enroll as you approach age 65 and beyond.

Maybe you want to apply as soon as you’re eligible. Maybe you’re continuing to work and like the health insurance you have now. Maybe you thought you could sign up anytime.

Different enrollment periods may apply at different times in your life.

But if you’re new to Medicare, you can ignore the enrollment period that gets the most hype on broadcast and cable TV, the annual open enrollment extravaganza, from Oct. 15 to Dec. 7. That’s for reviewing and changing coverage you already have; you can participate next year.

Sometimes you can ignore all enrollment periods

If you’re receiving Social Security benefits at least four months before you turn 65, you’ll be signed up automatically for Medicare. Your enrollment is effective at the beginning of your birthday month or the start of the previous month if your birthday falls on the first.

That includes Social Security Disability Insurance (SSDI). Most people who get disability benefits become eligible for Medicare after 24 months, regardless of age.

If you’re already enrolled in Medicare because of a disability, you’ll remain enrolled at 65. If you’re on SSDI but not yet eligible for Medicare, you’ll be enrolled automatically based on your age when you reach age 65.

Your Medicare card should arrive in the mail three months before your coverage starts.

But if you don’t get Social Security yet, you need to sign up for Medicare. To start, you can enroll only during one of the three periods, and if you miss deadlines, you could end up with late enrollment penalties and coverage gaps.

Initial enrollment centers around age 65

Unless you qualify for Medicare early because of a disability, the first time you’re eligible to enroll is during the seven-month initial enrollment period that starts three months before the month you turn 65 and ends three months after your birthday month. If your birthday is on the first of the month, your initial enrollment period shifts one month earlier.

Signing up before your birthday month means that your coverage takes effect on the first of the month you turn 65 or the beginning of the previous month if your birthday is on the first. If you enroll during your birthday month or in the three months afterward, coverage begins the first day of the following month.

You don’t have to sign up for Part A hospitalization and Part B doctor and outpatient coverage at the same time. You can enroll in either one or both during this period.

But if you’re still working and have health insurance from your job or your spouse’s job, you should consider applying for Part A during your initial enrollment period unless you want to keep contributing pretax money to an existing health savings account (HSA).

The reason? Medicare Part A is free if you’ve paid Medicare taxes for 40 quarters, the equivalent of 10 years. It can be secondary coverage to your work policy if you land in the hospital.

But you can’t make new health savings account contributions after you enroll in Medicare, so that can be grounds to hold off on Part A. If you’re eligible for premium-free Part A, you can apply whenever you want after your initial enrollment period.

When you’re ready to sign up for Part A, coverage becomes effective six months before you apply or goes back to the month of your 65th birthday.

You can delay Part B, which has a monthly premium, if you have health insurance through a company that employs at least 20 people. When you retire or otherwise lose that, you’ll qualify for an eight-month special enrollment period to sign up.

Other types of coverage, such as insurance through an Affordable Care Act (ACA) marketplace, the Consolidated Omnibus Budget Reconciliation Act of 1985 (COBRA), the military’s Tricare insurance or a retiree health plan, don’t qualify for a special enrollment period and won’t keep you from a late enrollment penalty if you go 12 months or more without Part B.

Special rules for Puerto Rico. Residents of Puerto Rico are enrolled automatically in Part A if they’re already receiving Social Security, but not Part B. Unless you or your spouse is still working and you have health insurance from that employer, you’ll need to sign up for Part B yourself during your initial enrollment period.

The other U.S. territories — American Samoa, Guam, Northern Mariana Islands and the U.S. Virgin Islands — have the same sign-up rules as U.S. states.

The easiest way to apply for Medicare is on the Social Security Administration website, not Medicare.gov. You can hop online 24/7 during your initial enrollment period to fill out the forms.

State Health Insurance Assistance Programs (SHIPs), federally financed but locally staffed in your state or territory, offer unbiased personalized help for prospective enrollees, their families and caregivers. The toll-free national number, 877-839-2675, can connect you with your local SHIP, or you can find your area’s SHIP through an online directory.

After your Medicare application is processed, your card and Welcome to Medicare package should come in the mail two weeks later. The earliest it will be effective is the month of your 65th birthday, the month before if you were born on the first of a month.

Working past 65? Special enrollment may apply

You have an extra opportunity to enroll in Part B after age 65 without a late enrollment penalty if you qualify for a special enrollment period. The most common reason is if you or your spouse still works and has employer health insurance.

You can enroll in Medicare at any time while you have that coverage and up to eight months after the employment or coverage ends, whichever is first. The coverage must be from a current employer.

You can sign up online for Part B during a special enrollment period, but you’ll need to submit a special form to show employment since your initial enrollment period ended.

Be careful about coverage gaps. Even though you qualify for a special enrollment period if you have health insurance from an employer of any size, you may have coverage gaps if you work for an employer with fewer than 20 people and you don’t sign up for Medicare during your initial enrollment period.

Coverage from most small employers becomes secondary to Medicare at 65, so it may not pay your bills after your birthday. Ask your employer about company rules. However, coverage from an employer with 20 or more staffers always pays before Medicare.

Special enrollment periods cover more than signing up for Part B after you retire. You can become eligible if you:

Are dropped from Medicaid.
Couldn’t enroll initially because of a natural disaster.
Move from your Medicare Advantage plan’s area.
Return to the U.S. after living abroad.
Were released from prison, among other reasons.

These exceptional circumstances require you to submit a special form. The length of time for each special enrollment period varies and is often two or three months.

If you lose prescription drug coverage from a work-related plan that is the equivalent of Medicare Part D or better, you’re also eligible for a two-month special enrollment period but don’t have to submit a form. Instead, you can go to Medicare’s Plan Finder to compare private stand-alone Part D plans or Medicare Advantage plans with drug coverage and purchase one.

General enrollment is your fallback position

If you didn’t sign up for Medicare Part B during your initial enrollment opportunity and you don’t qualify for a special enrollment period, your next chance to apply for Medicare is during the general enrollment period, Jan. 1 to March 31 each year.

If that’s you, you’re not alone.

From 2016 to 2021, about 105,000 people applied annually during the general enrollment period, according to the Centers for Medicare & Medicaid Services. Since 2023, meeting the requirements for a special enrollment period is easier, but around 75,000 boomers a year, about 2 percent of all who turn 65, were expected to sign up during general enrollment.

Your coverage begins the first of the month after you sign up. But you may have to pay a late enrollment penalty for the rest of your life.

Unlike during your initial enrollment period or a special enrollment period, you can’t apply online. To enroll in Part B, you must complete Form CMS-40B and mail it or return it to a Social Security office.

You can call the Social Security Administration at 800-772-1213, 8 a.m. to 7 p.m. weekdays in most U.S. time zones.

You can sign up during the general enrollment period if you missed your initial enrollment period and you don’t qualify for premium-free Part A. You must call the SSA to start the application process if you need to enroll in both Part A and Part B during a general enrollment period.

Once you get Parts A and B squared away, you’re eligible for your six-month, once-in-a-lifetime Medigap open enrollment period and a special enrollment period to buy Part D, or you can choose to shop for a Medicare Advantage plan.

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This story, originally published March 8, 2023, has been updated with additional information about the general enrollment period and other details.

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About the author

Kimberly Lankford is a contributing writer who covers Medicare and personal finance and now writes about insurance for The Wall Street Journal | Buy Side. She wrote about insurance, Medicare, retirement and taxes for more than 20 years at Kiplinger’s Personal Finance and has written for The Washington Post and Boston Globe. She received the personal finance Best in Business award from the Society of American Business Editors and Writers and the New York State Society of CPAs’ excellence in financial journalism award for her guide to Medicare.

About the reviewer

Xavier Vaughn, an AARP senior adviser for Medicare programs, previously worked at the National Council on Aging in Arlington, Virginia, and Missouri Connections for Health, based in Columbia, Missouri. He earned his master’s degree in public health from the University of Alabama at Birmingham.