Medicare Open Enrollment 2027 Ends December 7: The Decision Tree That Saves Real Money

Published October 5, 2026. Premium, formulary, and network details change annually — verify your specific plans at Medicare.gov. Educational information only — not financial advice.

Headlines about Medicare Open Enrollment tend to be about dates. The dates matter — but the money is in the decisions, and most people make them in ten minutes with a plan comparison tool they don't fully trust.

Here is the decision tree. Work it top to bottom, in order, before December 7.

The Window: October 15 – December 7, 2026

Open Enrollment for 2027 coverage runs October 15 through December 7, 2026. What you can do in this window:

• Switch from Original Medicare to Medicare Advantage, or back.
• Change Medicare Advantage plans.
• Change your Part D (drug) plan.
• Join, drop, or change a Part D plan if you have Original Medicare.

Every change you make takes effect January 1, 2027. And critically: formularies, networks, and premiums change every single year — so "I'm happy with my plan" is only true if you have checked that your plan didn't change under you.

Step 1: Which Path Are You On?

Start here, because the rest of the tree forks.

flowchart TD
    A[Medicare Open Enrollment<br/>Oct 15 – Dec 7, 2026] --> B{How do you get coverage?}
    B -->|Original Medicare<br/>Parts A and B| C{Do you want a<br/>Part D drug plan?}
    B -->|Medicare Advantage<br/>Part C| D[Compare Advantage plans<br/>network, MOOP, extras, drugs]
    B -->|Working coverage<br/>through an employer| E[Run Part B and Part D<br/>creditable-coverage check]
    C -->|Yes| F{Original Medicare plus<br/>Medigap supplement?}
    F -->|Yes| G[Pick a standalone<br/>Part D plan]
    F -->|No| H[Consider standalone Part D<br/>or an Advantage plan]
    D --> I[Model the year's total cost<br/>not just the premium]
    G --> I
    H --> I
    E --> I
    I --> J[Check IRMAA exposure<br/>two-year income lookback]
    J --> K[Coordinate with any<br/>Roth conversion before Dec 31]
    K --> L[Confirm or switch<br/>by December 7]

Step 2: Compare Total Annual Cost, Not the Premium

The advertised premium is the least informative number on the page. The number that matters is your total annual cost:

Premiums + deductible + copays on your actual drugs + out-of-pocket maximum exposure

A plan with a $0 premium and a $6,000 maximum out-of-pocket can cost a heavy prescriber far more than a $40/month plan with better drug tiers. Conversely, if you take two inexpensive generics, the low-premium plan usually wins.

The 2026/2027 improvements worth knowing:

• The Part D out-of-pocket cap is $2,400 for 2027 — once you hit it, covered drugs cost you $0 for the rest of the year.
• Insulin is capped at $35/month per covered insulin product.
• The old "donut hole" coverage gap was eliminated as of 2025.

Those caps protect you. But copays before the cap still differ wildly by plan — which is why the comparison has to use your drug list, not a generic average.

How to do it in 20 minutes: log in at Medicare.gov/plan-compare, enter your actual prescriptions and dosages, and sort by estimated annual cost including drugs. That single move catches most of the money people leave on the table.

Common miss: people compare drug plans on premium alone, then discover in March that their maintenance inhaler moved to a higher tier. Check the 2027 formulary, not the 2026 one — the document you have is already out of date.

Step 3: If You're on Medicare Advantage, Check Your Doctors

Advantage plans are networks. Every year, plans renegotiate contracts and providers drop out. Two things to verify before you do anything else:

1. Is your primary care doctor still in-network for 2027?
2. Are your specialists and your preferred hospital still in-network?

If the answer is no, switching from a plan that was great in 2026 is not disloyalty — it is the whole point of the annual window. Keep an eye on extras too (dental, vision, hearing, fitness), which are the main reason people choose Advantage, but weigh them against the network and the out-of-pocket maximum.

Step 4: Check Your IRMAA Exposure Before You Commit

IRMAA — the Income-Related Monthly Adjustment Amount — is the surcharge high-income beneficiaries pay on top of standard Part B and Part D premiums. Two things trip people up:

• It runs on a two-year lookback. For 2027 premiums, Medicare looks at your 2025 modified adjusted gross income.
• It is a cliff, not a phase-in. Crossing an income threshold by a dollar can raise both your Part B and Part D premium for the year.

If your 2025 income was elevated — a business sale, a large capital gain, a big Roth conversion — you may already be on track for an IRMAA surcharge in 2027. You cannot undo 2025. But you can avoid repeating it in 2026 (which sets 2028 premiums) — see Step 5.

If your income dropped because you retired, you may be able to file SSA Form SSA-44 to request a reduction based on a life-changing event. That form is underused and can be worth real money.

Step 5: Coordinate the Medicare Decision With Your Year-End Tax Moves

This is where Medicare and retirement tax planning collide, and where most advice stops short.

If you are in the Roth conversion window — retired, before RMDs and Social Security fully stack up — you are voluntarily generating taxable income while you control the amount. That is the point. But that income counts toward IRMAA two years later.

So the conversion decision and the Medicare decision are the same decision, run on different clocks:

Filling the 22% bracket with a conversion can be genuinely smart. Filling it and blowing past an IRMAA cliff is not — unless you ran the numbers and decided the long-term tax-free growth is worth the surcharge. The failure mode is not converting. It is converting without modeling the surcharge.

Model both sides in one place with the Roth conversion calculator and the Year-End Retirement Tax Checklist.

Step 6: If You're Still Working, Verify Creditable Coverage

If you (or your spouse) are still working and covered by an employer plan, you may be able to delay Part B without penalty — but only if the employer coverage is primary and creditable for drug coverage. Get the annual creditable-coverage notice from the plan and keep it. Miss this and you can owe a permanent Part B late-enrollment penalty for as long as you have Medicare.

Two rules of thumb:

• Coverage from a large employer (20+ employees) while you're an active employee is generally primary to Medicare — you can usually delay Part B.
• Coverage from a small employer or as a retiree is generally secondary — you usually should enroll in Part B.

When in doubt, call the plan and SSA before the window closes. This is one of the few Medicare mistakes that never goes away.

The Timeline (Put These on Your Calendar)

The last two lines sit together on purpose. December is when the Medicare decision and the tax decision meet — and when the only thing standing between you and a worse outcome is having modeled them in the same place.

Put Your Own Numbers Behind It

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• Free gives you the Social Security estimator, a basic projection, and the health-cost inputs — no credit card.
• Premium ($9/mo or $84/yr — one plan, every tool) adds the tax and Roth conversion tools, full Monte Carlo analysis across 1,000 scenarios, the healthcare and long-term care modeling, and the AI Retirement Advisor, which answers questions like "How much can I convert in 2026 before I risk an IRMAA surcharge in 2028?" using your saved plan.

If you have been waiting to try the tax tools or the Advisor, both are in the one plan, at $9.

Model your year-end and Medicare moves free → · See the $9 plan →

Your Next Step

1. This week: Log in to Medicare.gov/plan-compare and enter your real prescriptions.
2. Before your plan switch: Confirm your doctors and hospital are in-network for 2027.
3. Check your 2025 income against the IRMAA thresholds — and file SSA-44 if a life-changing event applies.
4. Before December 31: Size your Roth conversion with the IRMAA consequences modeled.
5. By December 7: Confirm your 2027 coverage. Do not let the window close by default.

⚠️ Educational information only. This article is not tax, legal, or financial advice. Medicare premiums, thresholds, and plan details change annually. Verify against Medicare.gov and SSA.gov before deciding. Consult a qualified professional about your situation.

Related Reading

• Medicare Open Enrollment 2027: What to Check Before December 7
• Social Security COLA 2027: Current Estimate Range and What It Means
• Year-End Retirement Tax Checklist 2026
• Retirement Healthcare Costs: What to Expect in 2026
• The 7 Most-Searched Retirement Questions of 2026