Medicare Enrollment Periods & Deadlines: The 2026 Calendar

Why Medicare Enrollment Deadlines Matter

Missing a Medicare deadline can cost you for the rest of your life. The government designed Medicare with specific enrollment windows; signing up outside them without a qualifying reason triggers late-enrollment penalties added permanently to your premiums.

This guide walks through every 2026 enrollment period in plain English. When in doubt, verify your situation at Medicare.gov or by calling 1-800-MEDICARE (1-800-633-4227), because individual circumstances — especially around employer coverage — affect your deadlines.

Initial Enrollment Period (IEP): Your First Chance to Sign Up

The IEP is the 7-month window around your 65th birthday: 3 months before your birthday month, your birthday month, and 3 months after. If your birthday is in June, your IEP runs March 1 through September 30.

During your IEP you can enroll in Part A (usually free) and Part B (monthly premium). Confirm the current Part B premium at Medicare.gov, as it adjusts annually.

Timing affects your start date: enrolling in the 3 months before your birthday month means coverage begins the first of your birthday month; enrolling during or after can delay coverage. Signing up early avoids a gap.

Annual Enrollment Period (AEP): October 15 – December 7

AEP runs October 15 through December 7 every year, with changes effective January 1. It is the primary yearly opportunity to review coverage.

During AEP you can switch between Original Medicare and Medicare Advantage, change Advantage plans, or join, switch, or drop a Part D plan.

Plan formularies, premiums, copays, and networks change year to year, so compare your current plan against alternatives each fall using the Plan Finder at Medicare.gov.

General Enrollment Period (GEP): January 1 – March 31

If you missed your IEP and do not qualify for a Special Enrollment Period, the GEP (January 1 – March 31) is another chance to sign up for Part A and/or Part B.

The catch: enrolling during GEP rather than your IEP typically means a Part B late-enrollment penalty — 10% for each full 12-month period you were eligible but not enrolled, lasting as long as you have Part B.

Exception: if you or your spouse had employer group coverage through active work, you may delay Part B without penalty and use a Special Enrollment Period when that coverage ends.

Medicare Advantage Open Enrollment Period: January 1 – March 31

The MA OEP (January 1 – March 31) is only for people already enrolled in a Medicare Advantage plan.

During it you may switch to a different Advantage plan or drop Advantage and return to Original Medicare (and add a Part D plan). You can make this change once.

It is a safety valve so people who enrolled during AEP can make one correction early in the plan year — for example, if a preferred doctor is not in-network.

Special Enrollment Periods (SEPs): When Life Events Change Your Options

SEPs let you enroll or change coverage outside standard windows after qualifying life events. The most common is for people who delayed Medicare because they or their spouse had employer coverage through active work — when that coverage ends, you generally have 8 months to sign up for Part B without penalty.

Other triggers include moving out of your plan's service area, losing Medicaid or Extra Help, or your plan losing its Medicare contract. The length and rules vary by event.

SEPs are not automatic — you usually need documentation. Contact Medicare or your SHIP counselor to confirm which SEP applies. SHIP counseling is free in every state.

Late-Enrollment Penalties: The Cost of Waiting

Part B: 10% surcharge on the standard premium for every full 12-month period you went without coverage, with no cap — a 3-year delay means a 30% surcharge for as long as you have Part B.

Part D: 1% of the national base beneficiary premium for each full month without creditable drug coverage, added to your premium permanently. Creditable coverage means drug coverage at least as good as standard Part D (e.g., some employer plans). Keep the annual notice confirming your coverage is creditable.

Bottom line: enroll during your IEP unless you have creditable employer coverage. If you do, get written confirmation and track when it ends so you can use your SEP on time. Confirm the rules at Medicare.gov or SSA.gov.