Important Medicare enrollment dates

When you’re approaching the eligibility window for enrollment in one of the many Medicare coverage plans, it’s important to thoroughly research the benefits and costs of each plan, but it’s probably even more important to make sure you enroll at the right time. Missing an enrollment date could cost you higher premiums down the line – or it could cost you coverage entirely.

If you’re eligible for premium-free part A

If you’re already receiving Social Security or Railroad Retirement Board benefits and you’re a U.S. resident, you won’t have to worry about your enrollment date, since the government automatically enrolls you in both Part A and Part B at age 65 (about three months prior to your 65th birthday, your Medicare card will arrive in the mail.)

Your only concern about timing would be if you declined Medicare Part B during the initial enrollment window. (Part B has a premium, and some eligible individuals choose not to purchase it.) If you do decline Part B, you might have to pay higher Part B premiums if you enroll later on. For each year that you don’t enroll, your premium will be 10% higher, unless the reason you declined Part B was that you were insured by an employer-sponsored health insurance plan offered by your (or your spouse’s) current employer.

If you are covered by a group health plan because you or your spouse is still working and you don’t need Part B, you’ll have another opportunity to enroll in Part B in the future. When your group coverage ends, you’ll have an eight-month window during which you can enroll in Part B. Keep in mind that it needs to be group health coverage from a current employer. Retiree coverage or COBRA will not allow you to delay Part B enrollment without a penalty.

Note that if the employer has fewer than 20 employees, you’ll need to enroll in Medicare Part B when you’re first eligible, as your Medicare coverage will be primary in that case and the employer plan won’t provide sufficient coverage if you don’t have Part B. So it’s important to discuss the details with your employer before deciding to delay your enrollment in Part B.

If you aren’t eligible for premium-free Part A

Although most Medicare beneficiaries receive Part A without a premium, some do not. If you or your spouse worked for at least 10 years and paid Medicare taxes during that time, you’ll be eligible for premium-free Part A. Otherwise, you’ll have a monthly premium that varies depending on how many quarters of work history you have¹ (the lower premium is applicable if you or your spouse had at least 30 quarters — 7.5 years — of work history).²

If you’re a new immigrant and at least 65 years old, you will be able to start purchasing Medicare after you’ve been lawfully present in the U.S. for five years. For those first five years, you can enroll in a plan through the health insurance Marketplace in your state, with income-based premium subsidies available. And the option to purchase coverage in the Marketplace with a premium subsidy continues even after you’ve been in the U.S. for five years and are eligible to purchase Medicare coverage (see questions A.6 and A.8 on this guidance from CMS). Income-based Marketplace subsidies are not available to people who are eligible for premium-free Medicare Part A, but they are available to people who have to pay a premium for Medicare Part A.

If you are 65 and eligible for Medicare but not receiving Social Security or railroad retirement benefits, you won’t be automatically enrolled in Original Medicare. Instead, you can enroll during one of three enrollment periods.

• Initial enrollment period – a seven-month window of time that begins three months before the month of your 65th birthday (if your birthday is the first of the month, your special enrollment period is still seven months long, but it’s shifted to begin and end one month earlier than the normal schedule). The date your coverage starts depends upon how early in the IEP you enroll. If you wait until the last four months of the IEP, your Part B coverage will take effect the first of the month after you enroll, although for most people, Part A will be backdated to the month you turned 65.
• General enrollment period – January 1 to March 31 of each year. Your coverage will begin the month following your enrollment.
• Special enrollment period – You can wait to enroll in Part B and not incur a premium hike if you had coverage through your job or your spouse’s job when you became eligible for Medicare. While you’re still covered, you can enroll in Medicare at any time – and for another eight months after you lose your group coverage or you (or your spouse) stop working.

For more information about signing up for Parts A and B, call Social Security at 1-800-772-1213. (TTY users, call 1-800-325-0778.)

If you have end-stage renal disease (ERSD)

Individuals who have been diagnosed with end-stage renal disease (ERSD) – and who have had a kidney transplant or are undergoing dialysis – are eligible for Medicare. Your enrollment date in Medicare will depend on the date you begin receiving dialysis or the date you receive a transplant. You may also receive a combination of coordinated coverage from your employer – or COBRA – and Medicare.

Medicare has outlined a number of scenarios to guide you through various coverage options.

Depending on state laws where you live, you may have access to a Medigap plan when you become eligible for Medicare (some states allow insurers to charge higher premiums for people under 65, and even higher premiums for people with ESRD).

Before 2021, ESRD patients were generally not able to enroll in Medicare Advantage plans, but this changed as of 2021, under the terms of the 21st Century Cures Act. So you can enroll in any Medicare Advantage plan available in your area, if you prefer that option, and premiums are not higher for people under 65. There are pros and cons to Medicare Advantage versus Original Medicare + Medigap + Part D, but if Medigap isn’t available in your state for a person under 65 with ESRD, or if the premiums are unaffordable, an Advantage plan might be the only viable way for you to have a cap on your out-of-pocket costs. Keep in mind that in every state, you’ll have a one-time opportunity to switch to a Medigap plan when you turn 65, without any medical underwriting.

If you’ve been diagnosed with ALS

If you have been diagnosed with Amyotrophic Lateral Sclerosis (ALS), you’ll be automatically enrolled in Medicare in the month you begin receiving Social Security Disability Insurance or a railroad disability annuity payment. Enrollees with ALS receive their Medicare card in the mail the month their disability benefits begin.

Legislation enacted in December 2020 eliminated the five-month waiting period for ALS patients to receive Social Security Disability Insurance. The Social Security Administration’s page confirms that this provision has been implemented and there is no longer a waiting period.

Enrollment in a Part D prescription drug plan is not automatic, but you’ll have an opportunity to select a Part D plan when your Medicare coverage begins. You can work with a Medicare broker or use Medicare.gov’s plan finder tool to find the plan that will best fit your needs.

You can opt to get your Medicare coverage via Medicare Advantage if that fits your needs, and there are no restrictions on eligibility for Medicare Advantage due to health history. Depending on state laws where you live, you may have access to a Medigap plan when you become eligible for Medicare, although some states do not require Medigap insurers to offer plans to beneficiaries who are under age 65, and many that do require this allow the insurers to charge much higher premiums for people under 65.

When do I enroll in Medicare Advantage?

If you want to enroll in a Medicare Advantage plan, you can do so when you’re first eligible for Medicare,  in a window that extends three months before or after the month you become eligible for Medicare (either when you turn 65, or in the 25th month of receiving Social Security Disability Insurance, or in the scenarios outlined above for people with ALS or ESRD).

You can also change to or from Medicare Advantage during Medicare’s Open Enrollment period, from October 15 to December 7 each year. There’s also a Medicare Advantage open enrollment period (January 1 to March 31) each year, during which you can drop Medicare Advantage and switch back to Original Medicare (and a Part D plan if you want one) OR switch to a different Medicare Advantage plan.

You may choose to:

• Change from Original Medicare to a Medicare Advantage plan – You can switch between October 15 and December 7.
• Change from a Medicare Advantage plan to Original Medicare – You can switch between October 15 and December 7 and also from January 1 to March 31. You also have the option of joining a Medicare Prescription Drug Plan to supplement your Original Medicare coverage. But be aware that Medigap plans (Medicare Supplemental insurance) are not guaranteed issue during this period unless you’re in your trial-right window (the first year of being covered under Medicare Advantage), are eligible for a special enrollment period, or you live in a state that has its own guaranteed-issue rules for Medigap plans.
• Switch from one Medicare Advantage plan to another – You can switch plans between October 15 and December 7, or between January 1 and March 31.

Ready to enroll in new Medicare Advantage or Part D coverage? Discuss your plan options right now with a licensed Medicare advisor. Call 1-844-309-3504.

When do I enroll in Medicare part D?

Your first opportunity to enroll in Medicare’s prescription drug coverage is when you’re first eligible for Medicare, during the seven-month window that starts three months before the month you turn 65. If you enrolled in Medicare due to a disability, you can enroll in a prescription drug plan during a seven-month window beginning three months before your 25th month of disability, and ending three months after your 25th month of disability.

It’s important to note that if you don’t enroll during the seven-month period when you’re first eligible, you may pay a late-enrollment penalty that will raise your Part D premium when you do decide to purchase coverage.

During the Open Enrollment Period mentioned above, you can also enroll in a Medicare Part D plan, switch to another Part D plan or leave Part D entirely. During the Medicare Advantage open enrollment period, you can switch from Medicare Advantage to Original Medicare, and also purchase a Medicare Part D plan at that point. Again, pay close attention to the dates as they affect your options.

• Between October 15 and December 7 – You can join a Part D plan, switch between Part D plans, or drop your Part D coverage.
• Between January 1 and March 31 – You can leave a Medicare Advantage plan and switch back to Original Medicare.  If you do, you’ll have an opportunity during this time to enroll in a prescription drug plan as well. You can also switch from one Medicare Advantage plan to another, which will likely have different integrated Part D coverage. But you cannot switch from one stand-alone Part D plan to another during this period.

Enrolling in Medicare supplement insurance (Medigap)

You must be conscious of your specified Medigap enrollment period, since it’s the best time to enroll and might be your only opportunity to enroll, depending on your medical history and where you live.

Under federal rules, the enrollment period begins on the first day of the month in which you are at least 65 and enrolled in Medicare Part A and B. Your Medigap open enrollment period continues for six months.

The timing for Medigap enrollment is pivotal. If you enroll within your six-month initial enrollment window, you can’t be denied Medigap coverage or be charged more for the coverage because of a pre-existing medical condition. But if you miss the initial enrollment period and don’t qualify for a special enrollment period, insurance companies have the option of denying the application or increasing the premiums based on the company’s underwriting requirements.

However, states can set their own rules for Medigap plans: Several states have rules that ensure access to Medigap plans even after the initial enrollment window ends; you can click on a state on this map to see details about state-based Medigap regulations.

Louise Norris is an individual health insurance broker who has been writing about health insurance and health reform since 2006. She has written dozens of opinions and educational pieces about the Affordable Care Act for healthinsurance.org. Her state health exchange updates are regularly cited by media who cover health reform and by other health insurance experts.

1. ”Costs” Medicare.gov. Accessed Nov. 5, 2024 ⤶
2. ”Sec. 1818(d)(4)(B)” Social Security Administration. Accessed Nov. 5, 2024 ⤶