Understanding Medicare Enrollment Periods: Key Dates and Deadlines

Medicare plays a crucial role in providing health coverage for Americans age 65 and older, as well as certain younger individuals with disabilities. But understanding when to enroll is just as important as understanding what Medicare covers. Missing critical Medicare enrollment periods can lead to higher costs, penalties, or even delays in getting the coverage you need.

This guide breaks down the key Medicare enrollment periods, their deadlines, and what you need to do during each one to ensure seamless access to care and avoid unnecessary expenses.

1. Initial Enrollment Period (IEP)

Your Initial Enrollment Period is your first opportunity to sign up for Medicare. It lasts seven months and includes:

• The three months before your 65th birthday
• The month of your birthday
• The three months after your birthday

During this time, you can enroll in:

• Medicare Part A (hospital insurance)
• Medicare Part B (medical insurance)
• Medicare Advantage (Part C)
• Medicare Prescription Drug Plan (Part D)

🔔 Tip: To avoid gaps in coverage or late enrollment penalties, it's best to sign up during the first three months of your IEP.

2. General Enrollment Period (GEP)

If you missed your Initial Enrollment Period, you can still sign up during the General Enrollment Period, which runs from January 1 to March 31 each year.

Coverage will begin on July 1, and you may face late enrollment penalties, especially for Part B and Part D.

3. Special Enrollment Period (SEP)

Certain life events qualify you for a Special Enrollment Period, allowing you to enroll in Medicare or make changes to your coverage outside of the regular windows. Some examples include:

• Losing employer or union coverage
• Moving to a new area not covered by your current Medicare Advantage or Part D plan
• Leaving incarceration
• Gaining or losing Medicaid eligibility

Each SEP has different rules and timelines, so it’s important to act quickly once you qualify.

✅ Example: If you are still working at 65 and covered by employer health insurance, you may delay enrolling in Part B without penalty. Once your employment ends, you have an 8-month SEP to enroll in Part B.

4. Annual Enrollment Period (AEP)

Also known as the Open Enrollment Period, this runs from October 15 to December 7 every year. During this time, Medicare beneficiaries can:

• Switch from Original Medicare to a Medicare Advantage plan (Part C)
• Switch back from Medicare Advantage to Original Medicare
• Join, switch, or drop a Part D (prescription drug) plan

Changes made during the AEP take effect on January 1 of the following year.

💡 Tip: Use this time to review your plan’s costs, coverage, and provider network. Your health needs may change from year to year, and so do Medicare plans.

5. Medicare Advantage Open Enrollment Period (MA OEP)

If you’re already enrolled in a Medicare Advantage plan, you have another opportunity to make changes during the Medicare Advantage Open Enrollment Period, which runs from January 1 to March 31.

During this window, you can:

• Switch to a different Medicare Advantage plan
• Drop your plan and return to Original Medicare (and possibly add a Part D plan)

However, you cannot switch from Original Medicare to a Medicare Advantage plan during this period.

6. Medicare Supplement Open Enrollment Period

For those considering a Medicare Supplement (Medigap) plan, the ideal time to enroll is during your Medigap Open Enrollment Period. This six-month period starts on the first day of the month you are both:

• 65 years old or older, and
• Enrolled in Medicare Part B

During this time, insurers cannot deny you coverage or charge higher premiums due to preexisting conditions. After this window closes, you may be subject to medical underwriting, which could limit your options.

Avoiding Late Enrollment Penalties

Failing to enroll in Medicare on time can lead to costly penalties:

• Part B Penalty: 10% increase in your monthly premium for each full 12-month period you were eligible but didn’t enroll.
• Part D Penalty: 1% of the national base beneficiary premium for every month you go without creditable drug coverage after your IEP ends.

These penalties may apply for life, so knowing your deadlines is essential.

Medicare offers multiple enrollment windows tailored to different life situations, but navigating them without guidance can be tricky. Missing a key date can mean higher premiums or coverage gaps. By staying informed about Medicare’s enrollment periods—and knowing which one applies to you—you can make confident, timely decisions about your healthcare coverage.

If you're unsure about your eligibility or deadlines, resources like Medicare.gov or trusted advisors like Medicare on Video can help guide you through the process.

Your health is too important to leave to chance. Plan ahead, know your dates, and make the most of your Medicare benefits.