Once a year, every Medicare member gets a chance to look at their plan and make changes. That window is called the Annual Enrollment Period, or AEP. In 2026 it runs from October 15 to December 7. If you skip it, you usually have to wait another year. Here is how to use it well.
What is the Medicare Annual Enrollment Period?
The Annual Enrollment Period (AEP) is the once-a-year window when most Medicare members can switch plans. It is also called the Medicare Open Enrollment Period. The dates do not change. AEP always runs October 15 through December 7.
Any changes you make take effect January 1 of the next year. So if you switch plans on November 1, 2026, your new plan starts January 1, 2027.
What can you change during AEP?
AEP is flexible. You can do any of these:
- Switch from Original Medicare to a Medicare Advantage plan
- Switch from Medicare Advantage back to Original Medicare
- Switch from one Medicare Advantage plan to another
- Switch from one Part D drug plan to another
- Add a Part D drug plan if you do not have one
- Drop your Part D plan
What you cannot change during AEP
This trips people up. AEP does not let you buy a new Medicare Supplement (Medigap) plan with no questions asked. In most states, you have to answer health questions and pass medical underwriting to buy a Medigap plan after your first six months on Medicare.
This matters because Medigap has its own enrollment rules, and they are stricter than AEP. If you want to know more, read our guide on Plan G vs Plan N or our Medicare Supplement page.
Why AEP matters every year
Plans change every year. Carriers can change the premium, the copays, the network of doctors, the list of covered drugs (the formulary), and the maximum out-of-pocket cost. Your needs change too. New prescriptions, new doctors, new diagnoses.
A plan that worked great last year may not be the best fit this year. AEP is your one easy chance to fix that without a big hassle.
The Annual Notice of Change letter
In late September each year, your plan must send you a letter called the Annual Notice of Change, or ANOC. It tells you everything that is changing about your plan for next year.
Most people throw it in the pile. Do not do that. Open it. Look at three things:
- Is your monthly premium going up?
- Are your copays for doctor visits, hospital stays, or prescriptions going up?
- Did anything important get removed, like a drug you take or a doctor you see?
If any of those answers is yes, you may want to shop around during AEP.
How to decide if you should switch
Here is a quick three-step check anyone can do at the kitchen table.
Step 1: List your stuff. Write down every doctor you see, every prescription you take, and what you paid for healthcare last year.
Step 2: Check your current plan against your list. Are your doctors still in network? Are your drugs still on the formulary at a good copay tier? Did your costs change?
Step 3: Compare to two or three other plans. You can do this on Medicare.gov, with an independent broker, or with our free Should I Switch tool.
Common AEP mistakes I see every year
Mistake 1: Picking the plan with the lowest premium. The cheapest premium often costs you more once you add up copays and drug costs. Total annual cost matters more.
Mistake 2: Following a TV ad. The plans on TV are not always the best fit for your zip code. Plan availability is very local.
Mistake 3: Doing nothing because the letter looks confusing. Even if you keep your current plan, you should at least look. Five minutes of comparing can save thousands.
Mistake 4: Waiting until December 6. The last week of AEP is busy. Phone lines back up. Brokers run out of time. Give yourself room.
What if you miss AEP?
If you miss AEP, you usually have to wait a full year. There are two exceptions.
The first is the Medicare Advantage Open Enrollment Period, which runs January 1 to March 31. If you are already on a Medicare Advantage plan, you get one more chance to switch to a different Advantage plan or go back to Original Medicare during that window.
The second is a Special Enrollment Period (SEP). Big life changes like moving, losing employer coverage, or qualifying for Medicaid can trigger a SEP outside of AEP.
What to do this fall
- Watch for your Annual Notice of Change letter in late September
- Make your list of doctors, drugs, and last year's costs
- Compare your current plan to two or three others by mid-November
- Make your switch (or stay) by early December
- Watch for your new plan ID card to arrive in late December
If any of this feels confusing, talk to an independent agent. The first conversation is free, and a good agent will not charge you anything for help comparing plans.