If you (or a loved one) have Medicare, October through early December is the big decision season. It is when you can change drug plans, switch Medicare Advantage plans, or move back to Original Medicare without having to explain why.

Medicare’s Annual Enrollment Period, often called AEP, runs October 15 through December 7 every year, including 2026. (Source: Medicare.gov) The catch is that deadlines are strict, and a few common mistakes can lock you into a plan that is too expensive or does not cover your medications until the next valid enrollment window.

An older adult at a kitchen table reviewing Medicare plan documents and a laptop, natural home lighting, candid photography style

Below is a plain-English calendar for AEP and the other common switch windows, plus a step-by-step checklist you can use to compare plans with confidence, without needing a dictionary.

Medicare AEP 2026: key dates

Annual Enrollment Period (AEP): October 15 to December 7, 2026

  • What you can do: Join, switch, or drop a Medicare Advantage plan (Part C). Join, switch, or drop a stand-alone Part D drug plan. Switch from Medicare Advantage back to Original Medicare (and usually add Part D).
  • When changes start: January 1, 2027 (for elections made during AEP).
  • Hard deadline: In most cases, your request must be received by December 7 to count.

Think of AEP like open enrollment at work. You can shop, compare, and change, but once the window closes, your options shrink.

Other Medicare switch windows

Medicare Advantage Open Enrollment Period (MA OEP)

January 1 to March 31 (each year)

  • Who it is for: People who are already enrolled in a Medicare Advantage plan on January 1.
  • What you can do: Switch to another Medicare Advantage plan, or drop Medicare Advantage and return to Original Medicare (and add a Part D plan if needed).
  • One-change rule: You can generally make only one change during this period.
  • What you cannot do: Join Medicare Advantage for the first time if you are on Original Medicare (unless you qualify for another enrollment period).

Special Enrollment Periods (SEPs)

SEPs are “life event” windows. The timing and rules vary depending on the trigger, but common examples include:

  • Moving outside your plan’s service area
  • Losing employer or union coverage
  • Qualifying for Extra Help or Medicaid changes
  • Living in or leaving a skilled nursing facility or long-term care facility

If something big changed this year, do not assume you have to wait for AEP. Ask whether you qualify for an SEP.

First-time Medicare windows (quick reminder)

If you are brand new to Medicare, your options often come from your Initial Enrollment Period (around when you turn 65) or other first-time eligibility windows. Those are separate from AEP, but they impact Medigap rights and timing.

A Medicare handbook and a notepad on a tidy desk next to a computer keyboard, warm indoor lighting, documentary photography style

AEP timeline you can follow

Here is a simple calendar-style workflow that keeps you from rushing on December 6.

Late September to early October: prep period

  • Make a list of your prescriptions (drug name, dose, how often).
  • Write down your preferred pharmacies.
  • List your must-have doctors and hospitals.
  • Pull last year’s usage if you can: specialist visits, labs, imaging, physical therapy, etc.
  • Check your mail for your plan’s Annual Notice of Change (ANOC) and Evidence of Coverage (EOC). These explain what is changing next year.

October 15 to early November: compare and narrow

  • Use the official Medicare.gov Plan Finder to plug in your medications and pharmacies and compare estimated total yearly costs.
  • Compare total yearly costs, not just premiums.
  • Verify your medications on each plan’s current formulary.
  • Check network status for your doctors and facilities.
  • Look closely at prior authorization rules and referrals.

Mid-November: confirm the details

  • Call the plan and ask the deal-breaker questions (see checklists below).
  • Confirm that your pharmacy is still preferred in 2027.
  • Double-check any big-ticket drugs for restrictions.
  • Watch your timing: if you are changing both a medical plan (Original Medicare or Medicare Advantage) and Part D, make sure you have drug coverage lined up for January 1 to avoid gaps.

By December 7: enroll and save proof

  • Submit your election (online, phone, or paper).
  • Save confirmation numbers, screenshots, or emails.
  • Watch for an acknowledgment letter from the new plan. If you do not receive one, follow up.
My personal rule: if the plan change matters, I treat it like booking flights. I do not wait until the last weekend, because “almost submitted” does not count.

Checklist: compare plans during AEP

You do not need to become an expert. You just need a repeatable process. Use these steps in order.

Step 1: Start with what changed

Before you shop, open your ANOC and look for:

  • Premium changes
  • Deductible changes
  • Copay and coinsurance changes
  • Maximum out-of-pocket changes (for Medicare Advantage)
  • Formulary changes, especially removals or new restrictions
  • Network changes
  • Pharmacy network changes

Step 2: Use Medicare.gov Plan Finder first

If you do only one thing, do this: use the Medicare.gov Plan Finder. It is the most reliable way to enter your specific drugs, dosages, and preferred pharmacies and compare estimated annual costs across plans.

Then, once you have narrowed it down to a short list, confirm the details with the plan (especially networks and medication restrictions).

Step 3: Compare Part D (or MA-PD) with a formulary-first approach

If medications are part of your life, treat the formulary like the grocery list. If the plan does not carry your items at a reasonable price, nothing else matters.

  • Confirm each medication is covered (not just “a similar drug”).
  • Check the drug tier. Lower tier often means lower copays, but not always.
  • Look for restrictions: prior authorization, step therapy, quantity limits.
  • Price by pharmacy. Many plans have preferred pharmacies with much lower copays.
  • Estimate your annual cost: premium + deductible + expected copays.
  • Understand the deductible: some plans have a deductible that applies to certain tiers only. This varies by plan.

Questions worth calling the plan about:

  • “Is my exact medication covered in 2027, and what tier is it?”
  • “Is prior authorization required for this drug?”
  • “Which nearby pharmacies are preferred, and how does pricing differ?”

Step 4: Compare Medicare Advantage by network, then costs

Medicare Advantage plans can be a good value when the network fits your life. The risk is picking a plan that looks cheap on paper but does not include your providers or makes care harder to access.

  • Verify your doctors are in-network for next year. Do not rely on last year’s status.
  • Verify your hospital and major clinic systems, especially if you have upcoming procedures.
  • Get clarity on the exact provider listing: ask the plan to confirm the specific location or medical group, and save whatever written confirmation you can.
  • Check the plan type (HMO vs PPO). PPOs often offer out-of-network coverage, but at higher cost. HMOs typically require in-network care except emergencies.
  • Look at the maximum out-of-pocket (MOOP). This is your worst-case cap on covered medical spending for the year, and it matters even more than the premium.
  • Review specialist access rules: referrals, prior authorization, therapy visit limits.
  • Do a realistic math test: add premium + your typical copays for primary care, specialists, labs, imaging, and urgent care.
  • Check extra benefits carefully: dental, vision, hearing, fitness. Useful, but do not let them distract from network fit and medical cost sharing.
An older couple sitting in a medical office waiting room holding paperwork and a smartphone, candid healthcare photography style

Where Medigap fits (and what it does not do)

This is one of the most confusing parts, so here is the plain-English version. I include it because many people use AEP to consider a switch from Medicare Advantage to Original Medicare, and then wonder how Medigap fits into that move.

Medigap is not an AEP switch

AEP is mainly for switching Medicare Advantage and Part D. You can usually apply for a Medigap (Medicare Supplement) policy at any time of year, but you may be subject to medical underwriting unless you have a guaranteed-issue right. Rules vary by state and company.

  • If you want to leave Medicare Advantage and go to Original Medicare, AEP can let you make that move.
  • Adding Medigap after that is separate. Depending on your state and situation, insurers may ask health questions and can deny coverage or charge more, unless you are in a protected window.
  • Part D is separate too: Medigap does not include drug coverage, so you typically need a stand-alone Part D plan. You can usually enroll in Part D during AEP, but make sure your drug coverage starts January 1.

Guaranteed-issue and trial rights (quick examples)

Guaranteed-issue protections can apply in certain situations, like losing certain coverage or leaving a Medicare Advantage plan under a “trial right” in some cases. The details are fact-specific and can vary by state, so confirm before you drop a plan.

Medigap comparison checklist

  • Confirm your rights: Are you in your Medigap Open Enrollment Period (usually 6 months after you enroll in Part B and are 65+), or do you have a guaranteed-issue right?
  • Know what is standardized: A Plan G from one company must cover the same core benefits as Plan G from another company (pricing and service can differ).
  • Compare premium stability: Ask about rate increase history and pricing method (attained-age, issue-age, community-rated, if applicable in your state).
  • Check household discounts if available.
  • Do not forget Part D: Medigap does not include prescription coverage, so you typically need a stand-alone Part D plan.

Bottom line: If you are considering a move from Medicare Advantage to Original Medicare plus Medigap, start early in AEP so you have time to research underwriting, guaranteed-issue rules, and costs.

Common AEP mistakes

These are the issues I see most often when people end up paying too much for a full year.

1) Shopping by premium only

A $0 premium Medicare Advantage plan can still be expensive if your copays are high or your MOOP is high. Same for Part D: a low premium plan can cost more overall if your main drugs are pricey on that plan.

2) Assuming your doctor is still in-network

Networks change. Always verify for the upcoming year, and confirm the exact provider location or group when possible.

3) Not checking pharmacy status

Preferred pharmacies can make a huge difference in Part D costs. The pharmacy you have used for years might not be preferred next year.

4) Missing restrictions on your medications

A drug being “covered” is not the same as “easy to get.” Prior authorization and step therapy can create delays and headaches.

5) Waiting until the last week

Procrastination is expensive in Medicare land. If you run into enrollment issues, need to confirm details, or have to correct personal information, there may not be time.

6) Enrolling twice by accident

Multiple enrollments can overwrite each other. In many cases, the last valid election is the one that sticks.

7) Dropping coverage without a replacement

Be careful about gaps, especially with Part D. Going without creditable drug coverage can lead to the Part D late enrollment penalty. Employer or union drug coverage may be creditable, but you want to confirm that in writing.

8) Thinking AEP guarantees a Medigap plan

AEP can help you switch away from Medicare Advantage, but it does not automatically guarantee you can buy any Medigap policy without underwriting. This is a big one.

A quick plan scorecard

If you are stuck between two plans, score them using the categories that actually affect your life:

  • Medications: Covered? Affordable? Any restrictions?
  • Doctors and hospitals: In-network? Easy access?
  • Total cost estimate: Premium + expected copays + deductible.
  • Worst-case protection: MOOP for Medicare Advantage, or Medigap premium stability if using Original Medicare.
  • Convenience: Referrals, prior authorization frequency, customer service reputation.

If one plan wins on medications and network fit, it is usually the smarter pick even if the premium is a little higher.

What to do today

  1. Find your ANOC for next year and circle anything that changed.
  2. Write your prescription list and your pharmacy preferences.
  3. List your must-have providers (primary care, specialists, preferred hospital).
  4. Block 60 minutes during the first two weeks of AEP to compare plans using the Medicare.gov Plan Finder.
  5. Enroll early and save your confirmation.

Smart Cent Guide note: This article is for education, not personal medical or legal advice. Medicare rules can be very fact-specific, so if you are unsure which window applies, check Medicare.gov, call 1-800-MEDICARE, or contact your local SHIP (State Health Insurance Assistance Program) for free, unbiased counseling.