Medicare generally offers an automatic renewal each year after the initial sign-up, although there are exceptions.

Some people have automatic enrollment in Medicare, while others have to register online, through the mail, or in person.

This article focuses on the details of initial enrollment and reenrollment for Medicare coverage. It also explains the enrollment periods, costs, and any penalties.

Glossary of Medicare terms

We may use a few terms in this piece that can be helpful to understand when selecting the best insurance plan:

  • Deductible: This is an annual amount that a person must spend out of pocket within a certain time period before an insurer starts to fund their treatments.
  • Coinsurance: This is a percentage of a treatment cost that a person will need to self-fund. For Medicare Part B, this comes to 20%.
  • Copayment: This is a fixed dollar amount that an insured person pays when receiving certain treatments. For Medicare, this usually applies to prescription drugs.
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As a general rule, once a person enrolls in Medicare, they do not have to reenroll annually. This is true for enrollment in Original Medicare, which is Part A and Part B, or a Medicare Advantage (Part C) plan that private insurance companies offer.

A person does not usually have to reenroll or fill out paperwork annually if they are satisfied with their coverage.

Learn more about Medicare Parts A and B.

Annual notice of change

In September each year, all Medicare Advantage companies send an Annual Notice of Change to people enrolled in their plans. The document outlines any potential coverage changes effective from the following January, including costs, coverage level, and service areas.

If a person is unsatisfied with the changes to their coverage, they may wish to enroll in a new plan or return to Original Medicare. A person can make these changes during the Medicare open enrollment period (OEP), which is from October 15 to December 7 every year. When a person selects a new plan, it will go into effect on January 1 of the following year.

Learn more about Medicare enrollment periods.

An exception to automatic Medicare reenrollment is when a person’s plan no longer offers services. In that case, a person can switch Medicare plans 2 months before the scheduled end date of their policy or up to 1 full month after the contract ends.

Another exception is if Medicare terminates the plan for underperformance. In this instance, the plan will usually stop offering coverage before the end of the calendar year. In that case, a person can enroll in a new Medicare plan during the period from December 8 until the last day in February.

There are several circumstances when someone may not have Medicare coverage, even when they are eligible. These situations may include when a person has any of the following circumstances:

  • having private insurance through an employer
  • living outside the United States
  • not paying premiums

If a person loses private insurance coverage, they can reinstate their Medicare plan during a special enrollment period (SEP).

Similarly, if a person moves back to the United States, they can reinstate their Medicare plan during a SEP.

If a person disenrolls from their Medicare plan for non-payment of premiums, they must usually wait until the next enrollment period to rejoin Medicare. As a general rule, this will be in the OEP between October 15 to December 7 each year.

Good Cause

The Good Cause policy is a grace period that allows someone to explain the reason for the non-payment of their plan premiums. Examples of Good Cause qualifications may include an emergency or unexpected financial burden.

The policy allows a person to get their coverage back without waiting for the next enrollment period. However, they must pay all their owed premium amounts within 3 months of disenrollment.

There are several times when a person can enroll in Medicare, including:

  • initial enrollment period (IEP)
  • Medicare Advantage enrollment period
  • OEP
  • SEP

Enrollment periods offer a person the opportunity to take various actions relating to Medicare, such as enrolling in Original Medicare (Part A and Part B), enrolling in new plans, making changes to a plan, or switching plans.


The IEP lasts for 7 months. It begins 3 months before a person turns 65, includes their birthday month, and continues for an additional 3 months.

Medicare Advantage enrollment period

The Medicare Advantage enrollment period lasts for 3 months, from January 31 to March 31 each year. During this time, people who already have a Medicare Advantage plan can switch to another plan or reenroll in Original Medicare.


The OEP, also known as the annual enrollment period, lasts from October 15 to December 7 each year. During this time, a person can make changes to Original Medicare, Advantage, and Medicare Part D prescription plans.


SEPs are periods when Medicare allows a person to make changes to Medicare plans depending on certain circumstances.

Learn about how to enroll for Medicare.

Medicare has penalties for being unable to enroll or for allowing coverage to lapse.

Part A

Not enrolling in Medicare Part A when a person is first eligible can result in a late enrollment penalty.

The Medicare Part A penalty is 10% of a person’s monthly premium, which varies depending on the amount of Medicare taxes paid. A person will pay the added premium for two times the number of years they could have signed up for Part A but did not do so.

For example, if a person delayed signing up for Medicare Part A for 2 years, they would pay the 10% premium for 4 years.

It is important to note they do not have to pay a penalty if they had private insurance during the time they could have had Medicare Part A.

Part B

Not enrolling in Medicare Part B when a person is first eligible can increase their monthly payment by 10% for each 12-month period they did not sign up.

Part D

If a person goes more than 63 days in a row without credible drug coverage, they may be subject to a Medicare late enrollment penalty.

The late enrollment penalty is not a one-time cost. Instead, a person pays the penalty as long as they continue with their Medicare-based prescription drug coverage. The penalty depends upon the number of months someone goes without Part D coverage.

To calculate this penalty, Medicare will multiply 1% of the national base beneficiary premium, which is $34.70 in 2024, by the number of full months a person did not have Medicare Part D. Medicare adds the cost to a person’s monthly Part D premium.

The penalty is subject to premium changes, so it can increase every year.

Learn more about Medicare enrollment penalties.

Medicare resources

For more resources to help guide you through the complex world of medical insurance, visit our Medicare hub.

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Typically, a person does not have to reenroll in their Medicare policy annually. If they are satisfied with their coverage, they do not have to notify Medicare or their insurance company.

However, an individual needs to pay attention to enrollment periods to ensure they do not let their coverage lapse, as they could be subject to costly late enrollment penalties.

If there are any major changes to plans, Medicare and Medicare Advantage will notify policy holders before the enrollment periods begin.