Medicare Enrollment Deadlines: When Can You Sign Up?

• 7 months around age 65

  Initial Enrollment Period (IEP)

  Starts 3 months before the month you turn 65, includes your birthday month, and ends 3 months after — 7 months total. This is when most people first enroll in Part A and/or Part B.

• Oct 15 – Dec 7

  Annual Election Period (AEP)

  Every year. Switch Medicare Advantage plans, move between Original Medicare and Medicare Advantage, or change Part D plans. Changes take effect January 1.

• Jan 1 – Mar 31

  Medicare Advantage Open Enrollment Period (OEP)

  If you're already in a Medicare Advantage plan, you can switch to a different Medicare Advantage plan or drop back to Original Medicare (and add a Part D plan) once during this window.

• 6 months, starts at 65 + Part B

  Medigap Open Enrollment Period

  Your strongest window to buy any Medigap policy without medical underwriting. Starts when you're 65 or older and enrolled in Part B.

• Varies by situation

  Special Enrollment Periods (SEPs)

  Triggered by specific events — losing employer coverage, moving out of your plan's service area, your plan leaving Medicare, or qualifying for Medicaid or Extra Help, among others. The window length depends on the SEP type.

What happens if I miss my enrollment window?

If you don't sign up for Part B when first eligible and don't have other creditable coverage (like an active employer plan), you can face a permanent late enrollment penalty of 10% of the Part B premium for every full 12-month period you were eligible but not enrolled — and you may have to wait until the next General Enrollment Period (January 1 – March 31) to sign up, with coverage starting the month after you enroll.

Part D has its own late enrollment penalty if you go more than 63 days without creditable drug coverage. See how that penalty is calculated →