Medicare Enrollment Periods Explained: When You Can Sign Up or Make Changes

TESTIf Medicare's calendar feels confusing, you're not alone. There are several "windows," each with its own rules about what you can do and when coverage starts.

Once you know which window applies to you, decisions get much simpler. Here's a plain-English guide for 2026 and 2027 from our office in Oklahoma City.

It's October: 2027 Plans Are Here

Starting October 1 each year, Medicare Advantage and Part D drug plans may begin marketing next year's plans. That's why the Medicare mail and TV ads just picked up.

If you're already in a Medicare Advantage or drug plan, your plan was required to send you an Annual Notice of Change (ANOC) by September 30. It lists what's changing for 2027, like premiums, copays, and covered drugs. Please don't toss it. It's the best way to tell whether your plan still fits.

Initial Enrollment Period (Turning 65)

Your first chance to sign up is your Initial Enrollment Period. It lasts 7 months: the 3 months before the month you turn 65, your birthday month, and the 3 months after.

When your coverage starts depends on when you sign up:

Premium-free Part A starts the month you turn 65.

Part B: If you sign up before your birthday month, coverage starts the month you turn 65. If you sign up during your birthday month or the 3 months after, coverage starts the next month.

If you already get Social Security benefits, you're generally enrolled automatically. Otherwise, sign up through Social Security at SSA.gov or 1-800-772-1213.

General Enrollment Period (January 1 – March 31)

Missed your Initial Enrollment Period and don't qualify for a Special Enrollment Period? You can sign up for Part B (and premium Part A) during the General Enrollment Period, January 1 – March 31 each year.

Your coverage starts the first day of the month after you sign up. You may