Medicare Enrollment Periods

There are a few different Medicare enrollment periods to know, which is one of the most confusing parts about the program.

But don’t worry! We’re going to explain what each common enrollment period is, when it is, and what product it is attached to.

Initial enrollment period

As you may have guessed by the name, this is the very first time you become eligible for Medicare.

For most, your initial enrollment period begins three months before the month of your 65th birthday and ends three months after.

If your birthday is on the first, however, your enrollment period will begin one month early.

So, for example, if your birthday is July 1 your initial enrollment period will begin on March 1. You’ll enroll online or contact Social Security for Medicare Part A and B.

If you are eligible for Medicare because you are already getting benefits from Social Security, you’ll get Medicare Part A and Part B automatically when you first become eligible and don’t need to sign up. Medicare will send you a “Welcome to Medicare” packet three months before you turn 65.

Medicare Supplement open enrollment

Once you are enrolled in Medicare Parts A and B, there is a six-month open enrollment period for Medicare Supplements (also known as Medigap). This is when you can enroll without any health questions and any pre-existing condition won’t affect your premium.

You can enroll in Medigap any time after this, but you’ll be subject to underwriting.

Annual election period

Every year Medicare has an open enrollment period known as the annual election period.

It begins on October 15 and ends on December 7.

During this time you can switch from Original Medicare to Medicare Advantage or vice versa. You can switch from one Advantage plan to another. You can switch Medicare Part D plans or enroll in one if you didn’t when you were first eligible (there will be a penalty for this, however).

Special enrollment period

There are lots of life events that trigger special enrollment periods. 

Just a few examples are:

  • Unintentional loss of coverage

  • Moving outside of a current plan’s service area

  • Got married

  • Had a baby, adopted a child, or got a child through foster care

  • Got divorced


Basically, if you have a significant life event that causes a loss of coverage or causes you to need an increase in coverage, it likely triggers a special enrollment period.

What happens if you miss your enrollment period?

There may be penalties if you miss your enrollment period.

Here are all applicable penalties:

  • If you do not enroll in Part B during initial enrollment, you’ll pay a late enrollment penalty. The penalty is an additional 10% of your premium for every 12-month period you should have had Part B. That 10% is applied each month for as long as you have coverage.

  • If you don’t have Part D coverage and miss your enrollment period, you’ll pay a late enrollment penalty. The penalty is an extra 1% of your premium each month for as long as you have coverage. 

  • If you do not qualify for free Part A coverage because you didn’t work long enough to be eligible and you miss your enrollment period, you’ll pay an additional 10% of your premium for twice the number of years you didn’t have coverage.


These penalties do not apply if you work beyond age 65 and continue to use your employer coverage instead of signing up for Medicare.

Once you decide to quit using employer coverage or retire, you will be eligible for Medicare during your special enrollment period.

This enrollment period is eight months long that begins either the month you or your spouse quits working or the month your group coverage ends, whichever comes first.

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