Medicare Open Enrollment 2026: AEP Deadlines and Cost-Benefit Checklist

Medicare AEP 2026: Key Dates and What You Can Change During the October 15–December 7 Window

Medicare open enrollment 2026 deadlines refer to the Annual Election Period (AEP) running from October 15 through December 7, 2026, during which beneficiaries can enroll in, switch, or disenroll from Medicare Part D prescription drug plans and Medicare Advantage plans for coverage starting January 1, 2027.¹ This window is the primary opportunity each year to adjust your prescription drug and medical coverage, and missing the December 7 cutoff means waiting until the next AEP unless a Special Enrollment Period applies.

The Medicare Annual Election Period for 2026 runs October 15 through December 7, 2026, allowing Part D and Medicare Advantage enrollment, plan switches, or disenrollment.¹ During this window, you can make three types of changes: switch from Original Medicare to a Medicare Advantage plan, switch from one Medicare Advantage plan to another, or drop your Medicare Advantage plan and return to Original Medicare. You can also join, switch, or drop a Medicare Part D prescription drug plan.

Changes made during AEP take effect on January 1, 2027. This is distinct from the General Enrollment Period (January 1 through March 31), which only covers Medicare Part A and Part B signups for those who missed initial enrollment — it does not allow Part D or Advantage plan changes.² The AEP is your single annual opportunity to optimize coverage, and the December 7 deadline is firm.

Why Annual Plan Review Matters More Than Your Initial Enrollment

Medicare Part D plans undergo annual formulary, premium, deductible, and network changes effective January 1 of the new plan year.³ A plan that was the best fit in 2025 may have a completely different drug list, higher premiums, or a narrower pharmacy network in 2026. Without an annual review, you could face unexpected out-of-pocket costs — for example, a common blood pressure medication that cost $10 in 2025 could move to a higher tier at $45 in 2026.

Medicare Advantage plans may change provider networks, drug formularies, and out-of-pocket maximums annually, requiring annual review during AEP.⁴ A specialist you relied on in 2025 might be out of network in 2026. The initial enrollment decision is important, but annual plan review is what protects your budget and access to care over the long term.

Medicare Advantage vs. Part D Plus Medigap: A Cost-Benefit Framework

Choosing between a Medicare Advantage plan and Original Medicare with a stand-alone Part D plan plus a Medigap policy requires comparing total annual costs across multiple dimensions. The table below outlines the key cost components for each option.

The cost-benefit analysis depends on your health status, preferred providers, and prescription drug needs. For a beneficiary with chronic conditions requiring multiple specialists, the higher monthly premium for Original Medicare plus Medigap may be offset by predictable out-of-pocket costs and nationwide provider access. For a generally healthy beneficiary who rarely sees a doctor, a $0-premium Medicare Advantage plan may offer adequate coverage at lower total cost.

The 7-Step Cost-Benefit Checklist Before You Switch Plans

Step 1: Review your Annual Notice of Change (ANOC). Your current insurer sends this by September 30 detailing any 2026 coverage or cost modifications.⁵ Read it carefully — it shows premium, deductible, and formulary changes.

Step 2: List your current prescriptions. Write down every medication, dosage, and frequency. Use Medicare's Plan Finder tool to check whether each drug is covered on 2026 formularies and at what tier.

Step 3: Estimate total annual drug costs. For each plan you're considering, calculate: monthly premium × 12 + deductible + copays for each prescription. Include any coverage gap (donut hole) costs.

Step 4: Check provider networks. If considering a Medicare Advantage plan, verify that your primary care physician and any specialists are in-network for 2026. Call the provider's office directly — online directories can be outdated.

Step 5: Compare out-of-pocket maximums. For Medicare Advantage plans, the maximum out-of-pocket for 2026 is $9,350 for in-network services¹. Compare this across plans and against your expected healthcare utilization.

Step 6: Factor in IRMAA surcharges. If your modified adjusted gross income exceeds certain thresholds, your Part B and Part D premiums will include an Income-Related Monthly Adjustment Amount. A Medicare Advantage plan's $0 premium may still result in higher total costs if IRMAA applies to your Part B premium¹.

Step 7: Make your decision by December 7. Enroll online through Medicare.gov, by phone at 1-800-MEDICARE, or directly through a plan's website. Confirm your enrollment before the deadline.

How to Read Your Annual Notice of Change (ANOC) for 2026

Beneficiaries receive an Annual Notice of Change (ANOC) from their insurer by September 30 detailing any 2026 coverage or cost modifications.⁵ The ANOC is a multi-page document, but three sections matter most. First, the "Changes to Your Monthly Premium" section shows whether your premium is increasing, decreasing, or staying the same. Second, the "Changes to Your Drug Coverage" section lists formulary changes — drugs added, removed, or moved to different tiers. Third, the "Changes to Your Provider Network" section (for Medicare Advantage plans) shows which doctors and hospitals are leaving or joining the network.

Compare the ANOC side by side with your current year's Evidence of Coverage document. If a drug you take is being removed from the formulary, you have until December 7 to switch to a plan that covers it. If your premium is increasing by $30 per month, that's $360 per year — potentially enough to justify switching to a lower-cost plan.

IRMAA Surcharges: How Your Plan Choice Affects Income-Related Premiums

The Income-Related Monthly Adjustment Amount (IRMAA) applies to Medicare Part B and Part D premiums when your modified adjusted gross income exceeds certain thresholds. For 2026, the standard Part B premium is $174.70 per month⁴, but IRMAA surcharges can add $69.90 to $419.30 per month depending on income level⁴. Part D plans also have IRMAA surcharges ranging from $13.70 to $76.40 per month⁵.

The most common IRMAA mistake is misunderstanding the two-year lookback rule. A 2026 Part B premium is based on the 2024 tax return — so a one-time capital gain in 2024 can trigger a $4,700/year surcharge in 2026.⁶ If you experienced a life-changing event (retirement, divorce, death of a spouse) that reduced your income, you can file an IRMAA appeal using Form SSA-44.

When comparing Medicare Advantage versus Original Medicare plus Medigap, factor IRMAA into the total cost. A $0-premium Medicare Advantage plan still requires you to pay the Part B premium, including any IRMAA surcharge. The total monthly cost is not zero — it is your Part B premium plus IRMAA.

Common Enrollment Mistakes to Avoid During AEP 2026

Mistake 1: Assuming your current plan is unchanged. Plans change formularies, premiums, and networks every year. Never auto-renew without reviewing your ANOC.

Mistake 2: Missing the December 7 deadline. Unlike some insurance deadlines, the AEP cutoff is firm. Late enrollment means waiting until the next AEP unless a Special Enrollment Period applies.

Mistake 3: Ignoring the coverage gap (donut hole). Even with the Inflation Reduction Act's changes, some Part D plans have different cost-sharing in the coverage gap. Check whether your medications fall into this phase.

Mistake 4: Choosing a plan based only on the premium. A $0-premium Medicare Advantage plan may have high copays for specialist visits or expensive drugs. Calculate total expected costs, not just the monthly premium.

Mistake 5: Not checking pharmacy networks. A Part D plan may cover your drugs but only at preferred pharmacies. If your local pharmacy is out of network, you may pay higher copays or full retail price.

Mistake 6: Switching Medigap policies without medical underwriting. Medigap enrollment outside initial eligibility or guaranteed issue windows requires health underwriting and medical questions may be asked.⁴ If you have a pre-existing condition, you may be denied or charged higher premiums.

Your Next Step

Open your mailbox or online portal and find your Annual Notice of Change from your current Medicare plan. Read the premium and formulary change sections before October 31. Then visit Medicare.gov, log into your account, and use the Plan Finder tool to compare 2026 plans side by side. Enter all your prescriptions and preferred pharmacy. If you find a plan with lower total costs or better drug coverage, enroll before December 7. If you need help, call your State Health Insurance Assistance Program (SHIP) for free, unbiased counseling.