Direct answer: A Medicare OEP and AEP checklist starts with one question: what plan are you in today? The Annual Enrollment Period (AEP) runs October 15 to December 7 and is open to everyone with Medicare. The Medicare Advantage Open Enrollment Period (OEP) runs January 1 to March 31 and only helps people who are already in a Medicare Advantage plan.
AEP for 2027 coverage opened on October 15, 2026. Any change you make by December 7 starts on January 1. For people in Medicare Advantage, winter brings a narrow second chance.
If you are reading this at the kitchen table, worried about a parent, take a breath. You have time, and nobody can make you switch plans on the phone today.
The two windows have names that sound alike, and that causes real mistakes. This Medicare OEP and AEP checklist shows what each window does and what to check before you change anything.
In my 18 years in insurance marketing, I have seen ads blur these two windows on purpose. An ad can say enrollment is still open in February. That is true only for some of the people watching.
What are AEP and OEP, in plain words?
AEP: the fall window for everyone
AEP runs October 15 to December 7 each year. Medicare.gov’s page on joining a plan lists what you can do in this window:
- Move from Original Medicare to a Medicare Advantage plan.
- Move from Medicare Advantage back to Original Medicare.
- Switch from one Advantage plan to another.
- Join a Part D drug plan or switch to a new one.
- Drop your Part D drug plan.
You can make more than one change during AEP. The last choice you make before December 7 is the one that counts. It starts January 1.
OEP: the winter window for Advantage members only
OEP runs January 1 to March 31. It is only for people already in a Medicare Advantage plan. You get one change in this window:
- Switch to a different Advantage plan.
- Or leave Advantage for Original Medicare. You can join a stand-alone Part D drug plan at the same time.
The change starts the first day of the month after the plan gets your request. If you have Original Medicare with a Part D plan, OEP does not apply to you.
Swipe sideways to see every column.
| AEP (fall) | OEP (winter) | |
|---|---|---|
| Dates | October 15 to December 7 | January 1 to March 31 |
| Who can use it | Anyone with Medicare | Only people in Medicare Advantage |
| How many changes | Several, the last one counts | One |
| Join Advantage from Original Medicare? | Yes | No |
| Switch drug plans only? | Yes | Only when leaving Advantage |
| New coverage starts | January 1 | First of the next month |
Why does Medicare have two windows?
Plans change every year. Premiums move. Drug lists change. Doctors leave networks. Your plan mails you an Annual Notice of Change each fall to show what is different for next year.
AEP gives you time to read that notice and react. OEP exists because some problems only show up in January. A new doctor is out of network. A drug now needs prior authorization, which means the plan has to say yes first. OEP gives Advantage members one chance to fix that early in the year.
What do the 2026 numbers say about switching back?
Leaving Advantage during OEP is allowed. But you take on the cost structure of Original Medicare. Here are the 2026 figures from Medicare.gov’s 2026 costs page:
- Part B premium: $202.90 a month. That is $2,434.80 a year. Most people pay this in Advantage, too.
- Part B deductible: $283 a year. After that, you pay 20% of most doctor bills.
- Part A hospital deductible: $1,736 per benefit period.
- Skilled nursing facility: $0 for days 1 to 20, then $217 a day for days 21 to 100.
Here is a worked example with no Medigap policy. Say a parent spends 6 days in the hospital, then 30 days in rehab at a skilled nursing facility.
Swipe sideways to see every column.
| Cost | 2026 amount |
|---|---|
| Part A deductible | $1,736 |
| Rehab days 21 to 30 (10 days at $217) | $2,170 |
| Total before doctor bills | $3,906 |
Then add 20% of the doctor bills once the $283 Part B deductible is met. Original Medicare has no yearly cap on that 20%. A Medigap policy can cover much of it. Getting one after your first window is the hard part, as the next section explains.
The fine print: what neither window fixes
Medigap. Neither AEP nor OEP opens a new Medigap window. Your Medigap Open Enrollment is a one-time 6-month period tied to Part B at 65. Outside it, in most states, an insurer can look at your health and turn you down. There are special cases, like trial rights and some state rules. Read Medigap open enrollment at 65 before you leave a Medigap plan.
Part D late penalty. Changing plans does not erase a late enrollment penalty already on your account. The 2026 national base premium Medicare uses to figure that penalty is $38.99. Our guide to the Part D late enrollment penalty and creditable coverage explains how the clock works.
IRMAA. If your 2024 income was above $109,000 (single) or $218,000 (joint), your 2026 Part B premium starts at $284.10, not $202.90. Your Part D bill adds $14.50 or more. No plan switch changes that. Social Security handles it, and our IRMAA appeal guide covers how to ask for a review.
A missed deadline. If you missed AEP, a Special Enrollment Period may still fit. Moving or losing other coverage can open one. Do not guess. Ask a counselor to confirm which one, if any, applies to you.
Should you really shop your plan every fall?
The usual advice says to shop your plan every AEP. Looking is smart. Switching every year is a different matter.
If you have Original Medicare and a Medigap plan
Trying Advantage can be a one-way door. OEP lets you come back to Original Medicare. It does not bring your Medigap plan back. In most states, a new Medigap policy is not guaranteed once your first window has closed.
If you are in Advantage and things work
Still read your Annual Notice of Change. Confirm your doctors stay in network for next year. Confirm your drugs stay on the list. If both check out, staying put is a fine choice.
If you get Extra Help or Medicaid
Different rules can give you more chances to change plans during the year. Ask SHIP which rules apply to you. Start with Extra Help and Medicare Savings Programs and Medicare Special Needs Plans.
Where the money goes
Here is the part most guides skip. Private plans pay agents and call centers when someone enrolls. In lead generation, the phone call is the product. That is why Medicare ads pile up from October to March.
From my years on the lead-gen side, I can tell you how those ads are built. An ad that hints at benefits you may be missing is made to make the phone ring. It is not made to match you to the right plan.
A scope of appointment form lists the products an agent may discuss with you. It is not a counseling session. It is not an enrollment either. Read it before you sign, even at a free lunch.
Medicare.gov’s fraud page says Medicare will not call you to sell a plan. A caller with an official-sounding name is still a seller. Free help comes from your State Health Insurance Assistance Program (SHIP). SHIP counselors do not sell plans.
Related: Medicare Advantage vs Original Medicare, Medigap vs Medicare Advantage, and Medicare enrollment windows and penalties.
Eight moves before December 7
- Write the decision in one sentence. For example: keep my plan, or move to a plan my heart doctor takes. If you cannot write it, you are not ready for a sales call.
- Read your Annual Notice of Change. Circle any change to premiums or copays. Note any doctor who leaves.
- List your doctors and hospitals. Add your pharmacy.
- List every drug with its dose. Include how often you take it.
- Run the Medicare Plan Finder. Enter your drugs and pharmacy. Compare total yearly cost, not just the premium.
- Save the results. Take a screenshot or print a PDF of the plans you compared.
- Check prior authorization rules. This matters most for specialty drugs and rehab stays.
- Call SHIP or 1-800-MEDICARE before you sign. Do it early. The last week of AEP is the busiest.
After you enroll
Keep your confirmation number. Watch for a letter from the new plan. Fill a prescription in early January to test the card. If a drug is not covered, ask the plan about an exception before you pay cash.
What not to do
- Do not give your Medicare number to someone who called you first.
- Do not drop a Medigap plan until the new plan confirms your start date in writing.
- Do not mix up 2026 and 2027 numbers. CMS released the 2026 figures on November 14, 2025. Watch for the next year’s update each fall.
Frequently asked questions
Can I join a Medigap plan during AEP?
Not as a federal right. AEP covers Medicare Advantage and Part D changes. Medigap follows its own timing, mainly the 6-month Medigap Open Enrollment that starts with Part B at 65. Outside that window, most states let insurers check your health and say no. Some states have their own rules. Check with your SHIP before you drop any plan.
Can I switch Part D plans in OEP if I have Original Medicare?
No. OEP is only for people already in a Medicare Advantage plan. If you have Original Medicare with a stand-alone Part D plan, your main chance to switch drug plans is AEP, October 15 to December 7. Some people qualify for a Special Enrollment Period, such as after a move. A SHIP counselor can check that for you.
What if I missed AEP?
You may still have options. A Special Enrollment Period can open after certain life events, like moving out of your plan’s area or losing other coverage. If you are in Medicare Advantage, OEP gives you one change from January 1 to March 31. Do not assume you qualify for anything. Call SHIP or 1-800-MEDICARE and ask.
Does changing plans in AEP lower my IRMAA bill?
No. IRMAA is based on your income from two years back, as reported on your tax return. In 2026, that means 2024 income. Social Security sets the amount, not your plan. If your income dropped after a life event, such as retiring, you can ask Social Security to review it. Our IRMAA appeal guide walks through that.
Is a free sales lunch the same as free counseling?
No. A sales event is run by people who earn money when you enroll. That does not make them dishonest, but it shapes what they show you. SHIP counselors give free, unbiased Medicare help and do not sell plans. Use SHIP first, then talk to an agent if you still want to.
Your next step
Find your Annual Notice of Change this week. Then book a SHIP appointment or open the Medicare Plan Finder with your drug list in hand. December 7 comes fast, and a calm hour in October beats a rushed call in December.
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