Medicare has several enrollment periods that allow you to enroll in or change your Medicare benefits. For individuals transitioning into Medicare, it is important to understand which enrollment period will apply to their situation and the window that it creates. Failing to apply during the appropriate enrollment period can lead to lapses in coverage and lifetime financial penalties.

Let's look at the six enrollment periods in the Medicare program.

1. Initial Enrollment Period (IEP)

This is the first opportunity for you to sign up for Medicare. This enrollment window begins 3 months prior to your 65th  birth month (or your 25th disability check) and extends to 3 months after your 65th birth month.

Example: If you’re turning 65 on September 27th, your IEP is June 1st-December 31st. 

2. Special Enrollment Period (SEP)

Most times, this is applied if you delayed enrollment into Medicare Part B while you were working past 65 for a large group employer (over 20 employees). Under this scenario, you are given 8 months from your last day of coverage to apply for Medicare Parts A and B.  However, be careful about waiting all 8 months before enrolling–if you go more than 63 days without creditable Part D coverage, you will enter the penalty phase.

Note: There are other times when a Special Enrollment Period might be applied. This happens when any of the following occur:

• Your plan leaves the market
• You enroll into a 5-star plan
• You move from your current service area
• You become eligible for Medicaid

The enrollment windows to address any of these changes vary based on the specifics of your situation.

3. General Enrollment Period

This is for those who missed their IEP or SEP.  Annually, from January 1st-March 31st, eligible individuals can apply for Medicare Part A (if you have to pay for it) and Medicare Part B.  Approved applications will begin coverage on July 1st of the calendar year in which they applied.

4. Medicare Supplement Open Enrollment Period

This is the opportunity for individuals to enroll in or change their Medicare supplement plan without having to answer any medical questions (underwriting). This enrollment period lasts 6 months from the date their Medicare Parts A and B become effective. For most, this will be the 6 months following their 65th birthday, but those under a Special Enrollment Period have up to 6 months after their Part B is effective to apply for their Medicare Supplement plan underwriting-free.

5. Annual Enrollment Period (AEP)

During this enrollment period, which occurs annually from October 15th-December 7th, current Medicare beneficiaries can change their Medicare benefits for the upcoming year. The most common changes include:

• Enrolling in Medicare Advantage for the first time
• Moving from a Medicare Advantage plan to another Medicare Advantage plan
• Changing from a stand-alone Part D plan to another

6. Medicare Advantage Open Enrollment Period

This enrollment period occurs annually from January 1st-March 31st.  Once you sign up for a Medicare Advantage plan, you are allowed to make a one-time change in your benefits. Changes allowed are:

• Moving from one Medicare Advantage plan to another 
• Returning to Original Medicare and adding a Part D plan

Any change will take effect the first of the month following your change request.  Once April 1st comes, no more changes are allowed unless an individual qualifies for a Special Enrollment Period. 

It is important that future Medicare enrollees and current Medicare beneficiaries understand the different dates and rules of the various enrollment periods. Making a mistake in enrollment or the opportunity to change can have a lasting impact. The best way to ensure a successful transition is to start early. Like the legendary basketball coach John Wooden said, “If you don’t have time to do it right, when will you have time to do it over?”

John Norce is the President of Medicare Portal and a contributing columnist for Advisor Today.