Medicare Enrollment Periods in 2026: Every Deadline Your Family Needs to Know

Medicare does not let you sign up whenever you want. There are specific windows -- called enrollment periods -- and each one allows different actions. Miss the right window, and your parent could face lifetime penalties, coverage gaps, or both.

The system is needlessly complex. There are five different enrollment periods, each with its own dates, rules, and consequences. If you're helping a parent manage their Medicare, here is the calendar you need, in plain English.

Initial Enrollment Period (IEP)

Who it's for: People turning 65 who are enrolling in Medicare for the first time.

When it happens: A 7-month window centered on your parent's 65th birthday:

• Starts: 3 months before their birthday month
• Includes: Their birthday month
• Ends: 3 months after their birthday month

Example: If your parent turns 65 in June 2026, their IEP runs from March 1 through September 30, 2026.

What your parent can do:

• Enroll in Part A (hospital coverage)
• Enroll in Part B (medical coverage)
• Join a Medicare Advantage plan (Part C)
• Join a Part D prescription drug plan

Why it matters: This is the most important enrollment window. Enrolling during the IEP means coverage starts as soon as possible, with no penalties. Enrolling early in the window (the first three months) means coverage starts on the first day of the birthday month. Waiting until later in the window delays coverage start by one to three months.

What happens if you miss it: If your parent does not have qualifying employer coverage, missing the IEP triggers penalties. The Part B penalty is a 10% premium surcharge for every 12-month period they could have had Part B but didn't -- and it never goes away. They also cannot enroll in Part B until the General Enrollment Period (January through March), with coverage not starting until July.

For a detailed walkthrough of the IEP timeline, see our Turning 65 Medicare Checklist.

Annual Enrollment Period (AEP)

Who it's for: Anyone already enrolled in Medicare who wants to change their coverage.

When it happens: October 15 through December 7 every year. Changes take effect January 1 of the following year.

What your parent can do:

• Switch from Original Medicare to a Medicare Advantage plan
• Switch from one Medicare Advantage plan to another
• Switch from Medicare Advantage back to Original Medicare
• Join, drop, or switch a Part D prescription drug plan

Why it matters: This is the annual "shopping window." Plans change their premiums, formularies, networks, and benefits every year. A medication that was $10 per month in 2025 might cost $50 per month in 2026 under the same plan because it was moved to a higher tier. A doctor who was in-network might no longer be.

What to review every October:

• Is each of your parent's medications still on the plan's formulary? At the same tier?
• Are their doctors still in-network (for Advantage plans)?
• Has the monthly premium changed?
• Has the annual out-of-pocket maximum changed?
• Did the plan add or remove benefits they care about?

Use Medicare.gov/plan-compare to compare options side by side.

Medicare Advantage Open Enrollment Period (OEP)

Who it's for: People who are already enrolled in a Medicare Advantage plan and want to make a change.

When it happens: January 1 through March 31 every year. Changes take effect the first of the month after the plan receives the enrollment request.

What your parent can do:

• Switch from one Medicare Advantage plan to a different one
• Drop their Medicare Advantage plan and return to Original Medicare (and enroll in a standalone Part D plan)

What your parent CANNOT do during this period:

• Switch from Original Medicare to Medicare Advantage (that requires the AEP)
• Enroll in Part D if they are on Original Medicare and don't already have drug coverage

Why it matters: This is the "buyer's remorse" window. If your parent enrolled in a Medicare Advantage plan during the AEP (October-December) and realized in January that their new plan doesn't cover their doctor or their pharmacy is out of network, this is their chance to fix it.

It is also important for families who realize their parent's Advantage plan is too restrictive. If your parent was denied a prior authorization or discovered their plan's network does not extend to the state where they spend winters, the OEP lets them switch plans or move back to Original Medicare.

One critical warning: If your parent drops Medicare Advantage and returns to Original Medicare during the OEP, they will want to apply for a Medigap policy. However, outside of the initial 6-month Medigap Open Enrollment Period (which happens once, when Part B first starts), Medigap insurers can use medical underwriting. This means they can deny coverage or charge higher premiums based on health history. Some states (like New York, Connecticut, and Massachusetts) have guaranteed-issue protections, but most do not.

General Enrollment Period (GEP)

Who it's for: People who missed their Initial Enrollment Period and do not qualify for a Special Enrollment Period.

When it happens: January 1 through March 31 every year. Coverage starts July 1.

What your parent can do:

• Enroll in Part A
• Enroll in Part B

Why it matters: The GEP is the safety net for people who missed their IEP and don't have employer coverage that would qualify them for a Special Enrollment Period. It works, but it comes with consequences:

• Coverage does not start until July 1, leaving a gap of three to six months without coverage
• The late enrollment penalty still applies -- your parent will pay a higher Part B premium for life

The GEP exists so that nobody is permanently locked out of Medicare. But it is a last resort, not a plan.

Special Enrollment Periods (SEP)

Who it's for: People who experience specific qualifying life events.

When it happens: Varies depending on the triggering event.

What your parent can do: Enroll in or change Medicare coverage outside the regular enrollment windows.

The most common Special Enrollment Periods

Losing employer coverage (the most important SEP for families). When your parent retires or loses employer group health coverage (from an employer with 20+ employees), they get an 8-month Special Enrollment Period to sign up for Part B without penalty. This window starts the month after employment ends or the month after employer coverage ends, whichever comes first.

This is the SEP that saves families from penalties. If your parent delayed Part B because they had employer coverage, this is how they enroll cleanly. They will need the employer to fill out Form CMS-L564 (Request for Employment Information) as proof.

Moving out of a plan's service area. If your parent moves and their Medicare Advantage plan does not cover the new area, they get an SEP to choose a new plan.

Qualifying for Extra Help / Low-Income Subsidy. Low-income beneficiaries who qualify for Extra Help can change their Part D plan once per quarter (January-March, April-June, July-September).

Losing Medicaid coverage. If your parent loses Medicaid eligibility, they may qualify for an SEP.

Plan quality issues. If your parent's plan has been given a low star rating (1 or 2 stars) by CMS, they may qualify for an SEP to switch.

Key SEP rules

• Not all SEPs allow all actions. Some only let your parent change drug plans, not switch between Original Medicare and Advantage.
• Documentation is usually required. Keep everything: termination letters, COBRA notices, employer HR confirmation.
• Call 1-800-MEDICARE (1-800-633-4227) to confirm eligibility for a specific SEP before taking action.

The enrollment periods at a glance

The deadlines that cost real money

Two enrollment mistakes create permanent financial consequences:

1. Missing Part B enrollment without qualifying employer coverage: 10% premium surcharge for every 12-month period delayed. Permanent. Read the full breakdown in our late enrollment penalty guide.

2. Missing Part D enrollment without creditable drug coverage: 1% of the national base beneficiary premium for every month without coverage. Also permanent. In 2026, that base premium is $36.78, so each month of delay adds about $0.37 per month to premiums for life. That sounds small, but 24 months of delay means an extra $8.83 per month -- $106 per year -- forever.

Keeping track of these windows is one of the most important things you can do as an adult child managing your parent's healthcare. If you want a printable enrollment calendar with month-by-month action items, plus deadline alerts and a penalty calculator, the Medicare Enrollment Guide puts it all in one reference for $14.