Medicare Enrollment Periods: When You Can Enroll or Change Coverage

Initial Enrollment Period

Your Initial Enrollment Period is the seven-month window around your 65th birthday: the three months before your birthday month, your birthday month, and the three months after. People who become eligible for Medicare through disability have their own initial window.

Enrolling earlier in the window generally means coverage starts sooner. Waiting until the later months can delay your start date.

Annual Enrollment Period

The Annual Enrollment Period runs from October 15 through December 7 each year. During this window you can join, switch, or drop a Medicare Advantage plan or a Part D plan, and changes generally take effect January 1.

This is the window most people use to review whether their current plan still matches their doctors, medications, and budget for the coming year.

Medicare Advantage Open Enrollment Period

From January 1 through March 31, people already enrolled in a Medicare Advantage plan can switch to a different Medicare Advantage plan or return to Original Medicare and add a standalone Part D plan.

This window is limited to one change and is not available to people who are in Original Medicare at the start of the year.

General Enrollment Period

The General Enrollment Period runs from January 1 through March 31 for people who did not sign up for Part B when first eligible and do not qualify for a Special Enrollment Period. A Part B late enrollment penalty may apply.

Special Enrollment Periods

A Special Enrollment Period can open outside the standard windows when certain events occur, such as moving out of your plan's service area, losing employer coverage, changes in eligibility for assistance programs, or a plan leaving your area.

Whether you qualify depends on your specific circumstances, and the length of the window depends on the triggering event. Eligibility must be verified rather than assumed.

Employer coverage considerations

If you or your spouse are still working and covered by an employer group health plan, the rules about delaying Part B without penalty depend on the size of the employer and how the coverage coordinates with Medicare.

Before delaying any part of Medicare, confirm with your benefits administrator whether your coverage is considered creditable, and keep documentation.

Late enrollment penalties

• A Part B late enrollment penalty may apply if you delay Part B without qualifying coverage, and it generally continues for as long as you have Part B.
• A Part D late enrollment penalty may apply after a continuous period without creditable prescription drug coverage.
• A Part A premium penalty can apply to people who must pay a premium for Part A and enroll late.

Effective dates

Effective dates depend on the window you use and when you complete enrollment. Annual Enrollment Period changes generally begin January 1, while Initial Enrollment and Special Enrollment effective dates vary based on the specific timing and reason.

Enrollment period comparison

Eligibility for a Special Enrollment Period depends on your circumstances and must be verified before you rely on it.

A note on urgency

Deadlines are real, but pressure tactics are not a substitute for a good decision. Take the time to compare coverage against your doctors, medications, and budget, and ask questions before you enroll.