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I didn't enroll in Medicare when I turned 65. Can I sign up later?

Yes, but you can enroll only at certain times. You may also have to pay a late enrollment penalty unless you qualify for what’s considered a special enrollment period (SEP).

While you’re eligible for Medicare at age 65, you’re automatically enrolled only if you’re already receiving Social Security or Railroad Retirement Board benefits at least four months before your 65th birthday. Otherwise, you need to take steps to sign up yourself. 

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When is the earliest I can enroll in Medicare?

Unless you qualify for Medicare before age 65 because of a disability, the first time you’re eligible to sign up is during your initial enrollment period (IEP), which begins on the first day of the month three months before the month you turn 65 and lasts for three months after your birthday month. This is different than an SEP.

So if you’re a few months past your 65th birthday, you still may be in your initial enrollment period. Where you are in your IEP determines when your Medicare coverage starts:

  • If you enroll during those first three full months before your birthday, your coverage begins on the first day of the month you turn 65 or the first day of the previous month if your birthday is on the first of the month.
  • If you sign up during the month you turn 65 or the three months after your birthday month, coverage begins on the first day of the following month.

The rules changed in 2023. Coverage used to be delayed two or three months if you signed up after your birthday month.

What if I’m past my initial enrollment period?

The enrollment rules are different for Medicare Part A, which provides coverage for hospitalization, than they are for Medicare Part B coverage, which helps pay for doctor and outpatient services.

If you qualify for premium-free Part A, like most people, you can sign up for that coverage during your initial enrollment period or any time after without a penalty. Your Part A coverage is retroactive for up to six months but no earlier than the month you turned 65.

Part B isn’t as flexible. If you missed your initial enrollment period, you may be able to sign up later without penalty if you qualify for a special enrollment period.

You can qualify for a special enrollment period if you or your spouse is still working and you have health insurance from that employer. This can’t be coverage from your former employer’s plan through COBRA, the federal Department of Veterans Affairs, military retiree health coverage from Tricare, a labor union retiree plan or any other retiree health plans. You or your spouse must be actively working for the company providing the insurance.

If so, you can delay signing up for Medicare while you have that coverage. And your SEP lasts from the time you turn 65 up to eight months after the employment or coverage ends, whichever occurs first.   

Starting in 2023, you may also qualify for a special enrollment period in other circumstances, including if you missed your initial enrollment period because of a natural disaster.

Does the size of my employer make a difference?

Yes. You won’t have to pay a late enrollment penalty if you or your spouse is still working and you have coverage from that active employer, but you could have coverage gaps depending on the size of the company.

Companies with 20 or more employees. The employer’s health insurance is primary coverage and Medicare is secondary coverage even after you turn 65. That coverage will pay medical bills before Medicare.

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Companies with fewer than 20 employees. The employer decides whether the company’s health insurance is primary or secondary to Medicare when employees or their spouses turn 65. In most cases, Medicare becomes the primary coverage at 65 and settles your medical bills first, and the group plan will pay for expenses and services it covers that Medicare doesn’t. If you didn’t enroll in Medicare at 65, you may have to pay for any medical expense you incur out of your own pocket.

The good news is you can qualify for a special enrollment period to sign up for Medicare anytime while you or your spouse is still working for the employer that provides the coverage or for up to eight months afterward, regardless of company size.

As long as you sign up while you’re still working or during the first month after you leave the plan, Part B coverage will begin on the first day of the month after you enroll or the first day of any of the following three months of your choice.

If you sign up during the remaining seven months after you or your spouse stops working, then your coverage begins on the first day of the following month. For example, if you stop working in April but you sign up for Part B in June, your coverage will begin in July.

Premium-free Part A coverage begins six months retroactively, but no earlier than the month you turn 65.

What if I don’t qualify for a special enrollment period?

You’ll be able to sign up during Medicare’s general enrollment period (GEP) — from Jan. 1 to March 31 each year — if you miss your initial enrollment period and don’t qualify for a special enrollment period.

Part A. If you have to pay premiums for Part A because you or your spouse has not paid enough quarters of Medicare taxes, this is when a GEP kicks in, allowing you to sign up even though you missed your initial enrollment period. But you may have to pay a Part A late enrollment penalty. However, people who qualify for premium-free Part A can sign up at any time after they’re eligible without penalty.

Part B. If you’ve passed or didn’t qualify for a Part B special enrollment period, this is also when you can sign up for Part B. But you may have to pay a separate Part B late enrollment penalty.

Before 2023, people who signed up during a GEP had to wait until July 1 for their coverage to begin. But coverage now takes effect the month after you sign up.

Keep in mind

Part D. The enrollment and penalty rules are different for Part D prescription drug coverage. If you have other prescription coverage considered at least as good as Part D, you won’t face a penalty.

If you missed your initial enrollment period and have what Medicare calls “creditable coverage,” you can usually delay signing up without risking a Part D late enrollment penalty if you buy a plan within two months of the end of your creditable coverage.

You also have more flexibility to sign up or change Part D plans more often if you qualify for Extra Help, the federal program that helps people with low incomes and assets pay Part D premiums and out-of-pocket costs. If you’re eligible for Extra Help, you can switch Part D plans as often as once a calendar quarter during the first three quarters of the year. And you won’t be subject to a late enrollment penalty. 

Medigap. The open enrollment period for private Medicare supplement policies is not dependent on age. If you’re 65 or older, it starts the first month you have Part B coverage and lasts for six months. During that time insurers can’t deny you coverage or charge you more for a preexisting condition.

You can apply for coverage at any time. But after that six months, Medigap insurers in most states can reject you or charge more because of your health.

Medicare Advantage. To enroll in Part C, better known as an all-in-one Medicare Advantage plan, you must first have Part A and Part B coverage. You can sign up during your initial enrollment period for Medicare. After that, if you’ve missed your initial enrollment period, you can sign up:

  • Oct. 15 to Dec. 7 with new coverage starting Jan. 1. That’s Medicare’s annual open enrollment period.
  • Jan. 1 to March 31 if you sign up for parts A and B during the same general enrollment period. New coverage starts the month after you sign up. This is different from the Medicare Advantage open enrollment period, also from Jan. 1 to March 31, when you can switch from one plan to another if you already have Medicare Advantage.
  • All year if you decide to enroll in a Medicare Advantage plan that receives a five-star quality rating and one is available in your area.

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