Based on Centers for Medicare & Medicaid Services (CMS) official guidelines — 2026.
Every year, millions of Medicare beneficiaries miss the opportunity to optimize their coverage simply because they don't fully understand how Medicare's enrollment periods work — or because they assume their current plan is automatically the best option for the coming year.
Medicare plans change every year. Premiums increase, drug formularies are updated, provider networks shift, and new plan options become available. A plan that was ideal in 2025 may be significantly less suitable in 2026. The annual Open Enrollment Period exists specifically to give beneficiaries the opportunity to review and adjust their coverage — but taking advantage of it requires knowing when it happens, what can be changed, and how to evaluate options systematically.
This guide covers everything Medicare beneficiaries need to know about enrollment periods in 2026 — including the Annual Enrollment Period, Special Enrollment Periods, and the decisions that have the largest financial impact on retirement healthcare costs.
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Medicare Basics — The Foundation
Before examining enrollment periods, a clear understanding of Medicare's structure is essential — because enrollment decisions depend entirely on which parts of Medicare you have and which you're considering.
The four parts of Medicare:
Medicare Part A covers inpatient hospital care, skilled nursing facility care following a qualifying hospital stay, hospice care, and some home health services. Most people receive Part A without a premium because they or their spouse paid Medicare taxes for at least 10 years during working years.
Medicare Part B covers outpatient medical services — physician visits, preventive care, diagnostic tests, durable medical equipment, and outpatient procedures. Part B requires a monthly premium. The standard Part B premium in 2026 is $185.00 per month, though higher-income beneficiaries pay more through Income-Related Monthly Adjustment Amounts (IRMAA).
Medicare Part C, known as Medicare Advantage, is an alternative to Original Medicare (Parts A and B) offered by private insurance companies approved by Medicare. Advantage plans must cover everything Original Medicare covers and typically include additional benefits such as dental, vision, and hearing coverage. Most plans include Part D drug coverage.
Medicare Part D provides prescription drug coverage. It is available as a standalone plan (for those with Original Medicare) or is often included within Medicare Advantage plans.
Medigap (Medicare Supplement Insurance):
Medigap policies are sold by private insurers to cover the out-of-pocket costs that Original Medicare doesn't pay — deductibles, coinsurance, and copayments. Medigap works alongside Original Medicare (Parts A and B) and cannot be used with Medicare Advantage.
The Annual Enrollment Period — October 15 to December 7
The Annual Enrollment Period (AEP) — also called the Fall Open Enrollment Period — runs from October 15 through December 7 each year. Changes made during AEP take effect January 1 of the following year.
What you can do during AEP:
During the Annual Enrollment Period, Medicare beneficiaries can switch from Original Medicare to a Medicare Advantage plan, switch from Medicare Advantage back to Original Medicare, switch from one Medicare Advantage plan to a different Medicare Advantage plan, join a Medicare Part D prescription drug plan, switch from one Part D plan to a different Part D plan, and drop Medicare Part D prescription drug coverage entirely.
What cannot be changed during AEP:
Medigap policies cannot be purchased or changed during the Annual Enrollment Period without medical underwriting (health screening) in most states. The Medigap Open Enrollment Period — when you can buy any Medigap policy without medical underwriting — occurs only once, during the six months after you first enroll in Medicare Part B at age 65.
Why reviewing coverage annually matters:
Insurance companies submit plan changes to CMS each year, and these changes take effect January 1. Your current plan may change its premium, its drug formulary (the list of covered medications), its provider network, its cost-sharing structure, or its additional benefits. The Annual Notice of Change letter — which your plan is required to send you by September 30 each year — summarizes these changes. Reading this letter carefully is the essential first step in annual coverage review.
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Special Enrollment Periods — When Life Changes Your Coverage Needs
Special Enrollment Periods (SEPs) allow Medicare beneficiaries to make coverage changes outside of the standard enrollment windows when specific qualifying life events occur.
Common qualifying events for Special Enrollment Periods:
Losing employer-sponsored health coverage is one of the most common SEP triggers. When you or your spouse retires and loses employer coverage, you have eight months to enroll in Medicare Part B without penalty — regardless of whether you apply for Social Security benefits.
Moving to a new address can trigger an SEP if the move takes you out of your current plan's service area, or if you move to an area where new plan options are available. You typically have two months before and two months after the move to make changes.
Gaining eligibility for Extra Help — the federal program that helps pay Part D costs for low-income beneficiaries — provides a continuous SEP, allowing enrollment or plan changes at any time.
Your plan being discontinued, losing its Medicare contract, or significantly changing its benefits can trigger an SEP that allows you to choose a different plan.
Moving into or out of a skilled nursing facility or nursing home provides an SEP during the stay and for two months after discharge.
The Medicare Advantage Open Enrollment Period — January 1 to March 31:
This separate enrollment period allows people already enrolled in a Medicare Advantage plan to switch to a different Medicare Advantage plan or return to Original Medicare (and join a standalone Part D plan) once between January 1 and March 31 each year. Changes take effect the first day of the month after the plan receives the enrollment request.
How to Evaluate Your Coverage During Open Enrollment
Systematic coverage review during the Annual Enrollment Period requires examining four key dimensions:
Step 1: Review your current plan's Annual Notice of Change
The notice your plan sends by September 30 details every change taking effect January 1. Pay particular attention to premium changes, changes to your specific medications' coverage tiers or costs, network changes that might affect your current doctors, and changes to additional benefits you use.
Step 2: Assess your actual healthcare usage from the past year
Your healthcare needs evolve — and your coverage should evolve with them. Review how many physician visits, specialist appointments, hospitalizations, and diagnostic tests you had. Identify which medications you take regularly. Consider whether any new conditions or treatments are anticipated in the coming year.
Step 3: Use Medicare's Plan Finder tool
Medicare's official Plan Finder at medicare.gov/plan-compare allows you to enter your specific medications and preferred providers to compare all available plans in your area. The tool calculates estimated total annual costs — premiums plus estimated out-of-pocket costs based on your actual medication list — making plan comparison significantly more accurate than comparing premiums alone.
Step 4: Evaluate the total cost of coverage — not just the premium
A plan with a $0 premium and high cost-sharing may cost significantly more annually than a plan with a modest premium and lower cost-sharing. Calculate total estimated annual cost including premium, deductibles, copayments, and coinsurance based on your expected utilization.
Part D Drug Coverage — The Annual Review That Saves the Most Money
For many Medicare beneficiaries, the annual review of Part D prescription drug coverage produces the largest potential savings — yet it is the review most commonly skipped.
Why Part D requires annual review:
Drug plans update their formularies annually. A medication that was on Tier 2 (preferred generic) in 2025 may be moved to Tier 3 (non-preferred) or Tier 4 (specialty) in 2026, dramatically increasing your cost-sharing. A drug that was covered may be removed from the formulary entirely. New generic alternatives may become available at lower cost tiers.
The Medicare Extra Help program:
Extra Help — also called the Low Income Subsidy — is a federal program that helps Medicare beneficiaries with limited income and resources pay for Part D costs including premiums, deductibles, and copayments. In 2026, Extra Help provides full or partial subsidy for Part D costs for eligible beneficiaries.
Eligibility is based on income and assets. Many seniors who qualify for Extra Help are not enrolled because they are unaware of the program or believe they don't qualify. Contact Social Security at 1-800-772-1213 or visit socialsecurity.gov/extrahelp to apply or check eligibility.
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Free Help Navigating Medicare — SHIP Counselors
Every state has a State Health Insurance Assistance Program (SHIP) that provides free, unbiased Medicare counseling from trained volunteers. SHIP counselors are not insurance agents and receive no commissions — they work solely in the beneficiary's interest.
SHIP counselors can help you understand your current coverage and how it will change, compare plans available in your area using the Medicare Plan Finder, understand your rights and protections as a Medicare beneficiary, identify programs that might help reduce your costs (Extra Help, Medicare Savings Programs), and navigate appeals if a coverage decision is disputed.
To find your local SHIP counselor: call 1-800-677-1116 (the Eldercare Locator) or visit shiphelp.org. During the Annual Enrollment Period (October 15 to December 7), SHIP counselors experience high demand — scheduling your appointment early in October is advisable.
Medicare Savings Programs:
Medicare Savings Programs are state-administered programs that help low-income Medicare beneficiaries pay for Part B premiums, deductibles, and cost-sharing. Four levels of assistance are available depending on income. Your State Medical Assistance (Medicaid) office administers these programs — contact information is available at medicare.gov or through your SHIP counselor.
Common Medicare Enrollment Mistakes — And How to Avoid Them
Delaying Part B enrollment when leaving employer coverage:
If you retire after age 65 and lose employer-sponsored coverage, you have only eight months to enroll in Part B without a late enrollment penalty. Missing this window results in a permanent 10% premium increase for each full 12-month period you were eligible but not enrolled — a costly mistake that cannot be reversed.
Assuming your current plan is automatically the best option:
Plan inertia — staying with the same plan year after year without review — is the most expensive Medicare mistake. Insurance companies count on beneficiary inertia, and plans that were competitive when you enrolled may become significantly less so as formularies and benefits change.
Comparing only premiums:
A $0 premium plan sounds attractive — but if your medications are on high cost-sharing tiers or your preferred physicians are not in-network, total annual costs may exceed those of a plan with a modest monthly premium.
Not checking whether your doctors are in-network:
Medicare Advantage plans have provider networks. If you switch plans without verifying that your current physicians accept the new plan, you may face significantly higher out-of-network costs or need to change providers.
Missing the Part D late enrollment penalty:
If you don't have creditable prescription drug coverage (coverage at least as good as Medicare's standard coverage) when you first become eligible and don't enroll in Part D, you will pay a permanent late enrollment penalty — 1% of the national base beneficiary premium for each month you delayed enrollment.
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Your Medicare Open Enrollment Action Plan
| Timing | Action |
|---|
| September | Read your Annual Notice of Change carefully |
| Early October | Schedule SHIP counselor appointment if needed |
| October 15 | Annual Enrollment Period begins |
| October–November | Compare plans using medicare.gov/plan-compare |
| Before December 7 | Make any coverage changes |
| December 7 | Annual Enrollment Period ends |
| January 1 | New coverage takes effect |
Key contacts and resources:
The official Medicare helpline is available at 1-800-MEDICARE (1-800-633-4227), available 24 hours a day, 7 days a week. The Medicare Plan Finder is located at medicare.gov/plan-compare. SHIP counseling assistance is available at shiphelp.org or by calling 1-800-677-1116. Extra Help applications can be submitted at socialsecurity.gov/extrahelp or by calling 1-800-772-1213. Medicare Savings Program information is available through your state Medicaid office.
This article provides general educational information about Medicare enrollment periods based on 2026 CMS guidelines. Medicare rules and plan details change annually. For personalized guidance specific to your situation, contact 1-800-MEDICARE or your local SHIP counselor.
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