Enrolling in Medicare isn’t always a one-and-done procedure. Once you become eligible, there are several points at which you can sign up for each of Medicare’s parts.

For most people, signing up for Medicare occurs during a 7-month initial enrollment period (IEP). The IEP starts 3 months before you turn 65 and continues for 3 months after your birthday.

Even with this time frame in mind, getting Medicare right can be confusing, and may also cost you in penalties if you get it wrong.

In this article, we’ll provide specific information about your eligibility and the time frame for signing up for Medicare.

If you’re currently receiving Social Security benefits and are under the age of 65, you’ll be automatically enrolled in Medicare parts A and B when you become 65. If you don’t wish to have Medicare Part B, you can decline it at that time.

If you’re not currently getting Social Security, you’ll have to actively enroll in Medicare.

Once you know the do’s and don’ts of signing up, the actual process is easy. The following factors are important to consider when enrolling in Medicare.

Your age

You may wish to put the wheels in motion by signing up for Medicare anytime during the 3 months prior to your 65th birthday. You can also sign up during the month you turn 65, as well as throughout the 3-month period following that date.

It’s important to note that if you delay signing up until the final 3 months of the IEP, the start of your medical coverage may be delayed.

If you have a disability

If you’ve been receiving either Social Security disability benefits or railroad retirement board disability benefits for at least 24 consecutive months, you’re eligible to enroll in Medicare at any time, no matter your age.

If you have amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, or end stage renal disease, you’re also eligible for Medicare at any time, independent of your age.

Your citizenship

In order to be eligible for Medicare, you must either be a U.S. citizen or a permanent U.S. resident who has lawfully lived here for at least 5 consecutive years.

If you have a spouse

Unlike private health insurance plans, your spouse can’t be covered under your Medicare plan.

In order for your spouse to be covered, they must meet Medicare’s specific eligibility requirements, such as age. Once those requirements are met, they may be eligible for some Medicare benefits based on your work history, even if they didn’t work.

If your spouse is younger than you and will be losing their health insurance once you go on to Medicare, they may be able to purchase health insurance through a private provider.

If you’re approaching 65 but would like to continue with the health insurance coverage you currently have through your spouse’s plan, you typically may do so, without penalty.

Medicare Part A

You’re eligible to enroll for Medicare Part A during the initial enrollment period.

You’ll automatically be enrolled at age 65 for Medicare Part A if you’re currently receiving Social Security disability benefits or railroad retirement board disability benefits.

Medicare Part B

As with Medicare Part A, you’re eligible to enroll for Medicare Part B during initial enrollment.

You’ll automatically be enrolled at age 65 for Medicare Part B if you’re currently receiving Social Security disability benefits or railroad retirement board disability benefits.

Medicare Part C (Medicare Advantage)

In order to enroll in Medicare Part C, you must first be eligible for, and have, Medicare parts A and B.

You may first sign up for Medicare Part C during initial enrollment or during open enrollment periods, which take place during the year.

You can also sign up for Medicare Part C during special enrollment periods, such as after the loss of a job that provided you with healthcare coverage.

You can enroll in a Medicare Advantage plan no matter your age, if you’re receiving Medicare benefits because of a disability, or if you have end stage renal disease.

Medicare Part D

You can enroll in a Medicare Part D prescription drug plan when you first get Medicare during initial enrollment. If you don’t sign up for Medicare Part D within 63 days of your IEP, you may incur a late enrollment penalty. This penalty will be added to your monthly premium each month.

You won’t have to pay a late enrollment penalty if you have prescription drug coverage through a Medicare Advantage plan or through a private insurer.

If you don’t like your current prescription drug plan, you can make changes to Medicare Part D during open enrollment periods, which occur twice a year.

Medicare Supplement (Medigap)

An open enrollment period for Medigap supplemental insurance is triggered by the start of the month during which you turn 65. Open enrollment for Medigap lasts for 6 months from that date.

During open enrollment, you’ll be able to buy a Medigap plan in your state for the same cost as people who have good health, even if you have a medical condition.

Medigap providers use medical underwriting to determine rates and eligibility. These vary from plan to plan and from state to state. When the open enrollment period ends, you may still be able to buy a Medigap plan, although your rates may be higher. There’s also no guarantee that the Medigap provider will sell you a plan outside of open enrollment periods.

Original enrollment

Original, or initial enrollment, is a 7-month period that starts 3 months before your 65th birthday, includes your birthday month, and ends 3 months after your birthday.

Medigap enrollment

The deadline for purchasing Medigap supplemental insurance at regular rates is 6 months after the first day of the month you turn 65.

Late enrollment

If you didn’t sign up for Medicare when you were first eligible, you can still enroll in Medicare parts A and B or in a Medicare Advantage plan during a general enrollment period, although penalties will most likely be added to the cost of your monthly premiums.

General enrollment takes place each year from Jan. 1 to March 31.

Medicare Part D enrollment

If you didn’t sign up for Medicare Part D when you were first eligible, you can sign up during an annual open enrollment period, which takes place from Oct. 15 to Dec. 7.

Medicare Advantage plans that include prescription drug coverage can also be purchased during an annual Medicare Advantage open enrollment period that takes place from Jan. 1 to March 31.

Plan change enrollment

If you wish to enroll in, drop out of, or change from your current Medicare Advantage (Part C) plan or Medicare Part D plan, you may do so at one of these open enrollment periods during the year:

  • Medicare Advantage open enrollment period: Jan. 1 to March 31
  • open enrollment period: Oct. 15 to Dec. 7

Special enrollment

Under certain conditions, you may be able to apply late for Medicare, during a period of time known as the special enrollment period. Special enrollment periods may be given if:

  • You waited to sign up for original Medicare because you were employed by a company that had more than 20 employees when you turned 65 and had health insurance provided for you through your job, union, or spouse. If so, you may apply for Medicare parts A and B within 8 months after your coverage ends, or for Medicare parts C and D within 63 days after your coverage ends.

Part D plans can be changed during special enrollment periods if:

  • You moved to a location that isn’t served by your current plan.
  • Your current plan has changed and no longer covers your geographic location.
  • You moved into or out of a nursing home.

Eligibility for Medicare usually occurs starting 3 months prior to the month you turn 65. This initial enrollment period lasts for 7 months.

There are special circumstances and also other enrollment periods provided for you, during which you may get coverage, if you miss initial enrollment.