Medicare Annual Enrollment Period: Dates, Rules, and What You Can Change

The Dates, and What December 7 Actually Means

The window opens October 15 and closes December 7. Both dates are the same every year, which makes them easy to remember and easy to plan around. Coverage you choose during this period starts on January 1 of the following year.

The detail people miss is how the deadline works. According to Medicare.gov, the plan has to receive your request to join by December 7. That is a deadline for the plan to get the request, not a date to start thinking about it. If you plan to enroll by phone, by mail, through Medicare.gov, or with the help of an agent, build in a few days of cushion so a delay on any side does not push you past the cutoff.

You can make more than one change during the window. If you pick a plan on October 20 and then find a problem with it on November 15, you can choose a different one before December 7. Generally, the last choice you make before the window closes is the one that counts. That flexibility matters because the fall mailings and plan details are not all in place on day one, and some of the most useful information, such as updated plan ratings, tends to become available partway through the period.

What You Can Change

Change	Allowed Oct 15 to Dec 7?	Takes effect
Original Medicare to Medicare Advantage	Yes	January 1
Medicare Advantage back to Original Medicare (add Part D)	Yes	January 1
One Medicare Advantage plan to another	Yes	January 1
Join, drop, or switch a standalone Part D plan	Yes	January 1
Switch Medigap plans	Not as a right; separate rules	Depends on the insurer and your state

The Annual Enrollment Period is mostly a Medicare Advantage and Part D event. Here is what it lets you do.

• Switch from Original Medicare to a Medicare Advantage plan.
• Switch from a Medicare Advantage plan back to Original Medicare. If you do, you can usually add a standalone Part D prescription drug plan at the same time.
• Switch from one Medicare Advantage plan to another, with or without drug coverage.
• Join, drop, or switch a standalone Part D plan if you have Original Medicare.

That list covers most of the decisions people face. For a closer look at how the pieces fit together, our overview of Medicare Advantage plans and our page on Medicare Part D explain what each one is built to do.

One point deserves emphasis: dropping to Original Medicare is a bigger decision than it sounds, because Original Medicare by itself has no yearly limit on what you pay out of pocket. Many people pair it with a Medicare Supplement plan, also called Medigap, and that is where the next section matters.

What the Annual Enrollment Period Does Not Cover

Medigap is not part of the Annual Enrollment Period. Medicare Supplement policies are sold by private insurers under rules that are separate from the fall window. You can apply for a Medigap policy at any time of year, according to KFF, but whether the insurer must accept you depends on your timing and, in most cases, on your state’s rules and your health.

The one time Medigap is guaranteed for most people is the six-month Medigap open enrollment period that starts when you are 65 or older and enrolled in Part B. After that period, insurers in most states can ask health questions and may decline an application or charge more based on the answers. A few states add extra protections, and a few federal guaranteed-issue situations exist, but these are specific and worth checking before you act. Our page on the Medigap open enrollment period and the guide to changing your Medigap policy go through those rules.

The practical takeaway is this. If you are on a Medicare Advantage plan today and you are considering a return to Original Medicare plus a Medigap policy, do not assume you can pick up a Medigap policy the same way you can pick up a drug plan. Check what the Medigap insurer will require before you cancel anything. Likewise, if you already have Medigap, the fall window does not give you a way to switch Medigap plans without answering health questions in most situations.

It also does not cover people who are not yet on Medicare. If you are turning 65, you are working from your own Initial Enrollment Period, which has a different set of dates. Our turning 65 guide covers that timeline.

Why Change Anything? Plans Change Every Year

Medicare Advantage and Part D plans are contracts that renew on a calendar-year basis. Each plan can adjust its premium, its deductible, its copays, the drugs on its formulary, the doctors and hospitals in its network, and the extra benefits it offers. Your plan does not need your permission to do that, and the plan you chose last year is not guaranteed to look the same this year.

That is why the fall is a review season rather than a decision season. Plans must send you an Annual Notice of Change by September 30, and a more detailed document called the Evidence of Coverage generally follows by mid-October. Those documents tell you what is different. If you have not opened them, set aside an hour and do so before you decide to stay put. Read the notice from the front, because the changes to costs, drugs, and networks are summarized in the first pages.

KFF has reported that nearly seven in ten Medicare beneficiaries did not compare their coverage options during a recent open enrollment period. For many, staying put is the right call, and nothing about this season says otherwise. But staying put is best when it is a choice you made after looking, not a default you drifted into because the paperwork seemed long.

How the Window Works for Each Kind of Coverage

The same seven weeks mean different things depending on what you have today. Find the description that matches you.

If you have Original Medicare and a standalone Part D plan, the window lets you change your drug plan, or move into Medicare Advantage. Your Part A and Part B coverage does not change, and you can keep seeing any doctor who accepts Medicare. The main thing to review is whether your drug plan’s formulary, tiers, and pharmacy network still suit your medications.

If you have Original Medicare, a Medigap policy, and a Part D plan, the same applies to the drug plan. Your Medigap policy renews on its own terms, separate from this window, and the insurer can change its premium but generally cannot cancel the policy as long as you pay it. The fall window is a good time to check your drug coverage, while your Medigap review follows a different calendar. Our guide to Medicare Supplement plans explains how those policies work.

If you have a Medicare Advantage plan that includes drug coverage, the window lets you stay, switch to another Medicare Advantage plan, or go back to Original Medicare and add a standalone drug plan. One caution applies here. If you have an HMO or PPO Medicare Advantage plan that includes drug coverage and you join a separate standalone drug plan, Medicare.gov says you will be disenrolled from your Medicare Advantage plan, health coverage included, and returned to Original Medicare. Ask before you sign up for a separate drug plan, so you know what will happen to the plan you have.

If you have employer or retiree coverage, or coverage through TRICARE or the VA, the right move depends on what that coverage is and whether it counts as creditable drug coverage. Dropping or changing it without checking can leave you with a gap or a permanent late penalty. We cover those situations in our guides to Medicare while still working and TRICARE For Life. We are an independent agency, not affiliated with the VA, TRICARE, or the Department of Defense, so confirm details with them.

Step by Step: From Decision to January 1

Here is the process in order, with what to expect at each point. The table after the list lays out the calendar for the fall.

• Early fall: look for the Annual Notice of Change from your current plan. It is due by September 30.
• Mid-October: the window opens on October 15, and your plan’s Evidence of Coverage is due around then. Plan ratings and updated plan information are generally available through Plan Finder in this period.
• October through November: compare plans using your drug list, your doctors, and how you use care. Choose a plan and enroll. You can enroll through Medicare.gov, by phone with the plan, or with a licensed agent.
• Right after enrolling: save the confirmation number or confirmation page. If you enroll by phone, write down the date, time, and name of the person.
• By December 7: the plan must have received your request. Do not treat this as a day to start.
• Mid to late December: you should receive a welcome packet and member ID card from a new plan. If you are staying put, you may receive nothing beyond the normal renewal materials.
• January 1: new coverage starts and your old plan ends. Present your new card at your first appointment or pharmacy visit.
• January through March: if you are in a Medicare Advantage plan and something is wrong, the Medicare Advantage Open Enrollment Period offers one change.

Date	What happens
By September 30	Plans must deliver the Annual Notice of Change
October 15	The Annual Enrollment Period opens; Evidence of Coverage due around this time
December 7	The plan must have received your request
January 1	New coverage starts and your old plan ends
January 1 to March 31	Medicare Advantage Open Enrollment Period, for Medicare Advantage enrollees

Enrolling in a new Medicare Advantage or Part D plan generally ends your old one, so you do not need to cancel it separately. If you join by phone, ask the representative to read back the plan name, type, and start date.

After December 7: What Second Chances Exist

Missing the window is not the end of the road, but it narrows your options. There are two main fallbacks.

The first is the Medicare Advantage Open Enrollment Period, which runs from January 1 through March 31. It applies only if you are already enrolled in a Medicare Advantage plan. During that window you can switch to a different Medicare Advantage plan or return to Original Medicare and add a drug plan. According to Medicare.gov, coverage generally starts the first of the month after the plan gets your request. It does not let you move from Original Medicare into Medicare Advantage, and it generally allows one change.

The second is a Special Enrollment Period, which is available only when something specific happens. Common triggers include moving out of your plan’s service area, losing other coverage, qualifying for or leaving Medicaid or Extra Help, or your plan leaving your area. If your plan’s contract with Medicare is not renewed, Medicare.gov says the window runs from December 8 to the last day of February. Another example is the Special Enrollment Period tied to a five-star rated plan. According to Medicare.gov, you can use it once a year, between December 8 and November 30 of the following year, to switch into a five-star plan if one is available where you live. Treat the rating as one input among several rather than a verdict.

If neither applies, you may be locked into your plan until the next fall window. That makes the weeks between October 15 and December 7 more consequential than they look on a calendar.

Costly Mistakes to Avoid

Most expensive Medicare enrollment mistakes are not about complicated rules. They come from assumptions. These are the ones we see people run into, along with what to do instead.

• Assuming your doctor is covered. A new plan may not include your doctor, or may include the doctor at a different location. Check the network with the plan and the office before you enroll, not after. Call the doctor’s office with the exact plan name and ask.
• Leaving Original Medicare and a Medigap policy without checking whether you could return. In most states, getting a Medigap policy later may involve health questions. If you cancel a policy you have and then want it back, the insurer may decline you or charge more. Look into this before you cancel.
• Choosing a plan for one extra benefit. A dental or fitness allowance can be appealing, but it should not outweigh a plan that leaves out your doctors or does not cover your drugs.
• Skipping the drug check. A drug moving to a higher tier or gaining a restriction is among the most common reasons for a bad January. Check each medication, with its dose, rather than only the ones you take most.
• Waiting until the last day. If the plan has to receive your request by December 7, a snag on December 6 can push you past the deadline. Leave yourself days of cushion.
• Dropping drug coverage without a replacement. If you go without creditable prescription drug coverage for a stretch of 63 days or more after you are first eligible, you may owe a late enrollment penalty for as long as you have Part D. Do not drop drug coverage unless you know you have another source that counts.
• Answering unsolicited calls or mailings. The fall is a busy season for scams as well as legitimate marketing. Our guide to Medicare fraud and scams explains what to watch for. Never give your Medicare number to a caller you did not expect.
• Assuming that no letter means no changes. Plans must send the notice, so a missing letter is a reason to ask for it, not a sign that nothing changed.

Three Pictures of How This Can Play Out

These are hypothetical examples meant to show the reasoning, not real cases. Medicare coverage is individual, so spouses choose plans separately and need not pick the same one.

Picture a retiree with Original Medicare, a Medigap policy, and a standalone drug plan. Her drug plan’s notice says that one of her medications is moving to a higher tier. She enters her drug list in Plan Finder, finds that a different drug plan covers all her medications at a lower cost, and switches that plan before December 7. She leaves her Medigap policy alone, because it is not part of the window and she is happy with it. Her review took an evening.

Picture a man in a Medicare Advantage HMO. His plan’s notice says his cardiologist’s group will no longer participate. He checks other plans in the county. One includes his cardiologist, but its hospital cost-sharing is higher and its premium is a bit more. He weighs the cost against his need to keep the same specialist, and he calls the cardiologist’s office and the plan to confirm network status before enrolling. He decides the continuity is worth the added cost. Someone else with the same notice might have decided differently, and either choice would be reasonable.

What to Gather and What to Ask

Before you sit down to compare, gather these:

• Your Medicare number and your current plan’s name and member ID.
• The Annual Notice of Change and, if it has arrived, the Evidence of Coverage.
• A list of your medications with doses and how often you take them.
• The names and office locations of your doctors, plus your hospital and pharmacy.
• A rough tally of how you used care this year, including any hospital stays, emergency visits, specialist visits, and tests.

When you talk to a plan or an agent, useful questions include:

• Are my doctors and my hospital in this plan’s network, at these locations, for next year?
• Are all my drugs on the formulary, at what tier, and with what restrictions?
• What is the plan’s yearly limit on what I pay for covered medical services, and what does it exclude?
• Which services require prior authorization or a referral?
• If I need to leave the plan later, what are my options and what would I give up?
• Will I get a confirmation, and when does coverage begin?

Write the answers down next to each plan so you can compare them later.

If Something Goes Wrong

Mistakes happen, and some can be repaired. The right fix depends on timing.

If you notice a problem before December 7, you can generally enroll in a different plan during the window, and the last choice you make before the deadline is the one that counts. That is the cleanest repair, so use it.

If you notice after December 7 and you are in a Medicare Advantage plan, the Medicare Advantage Open Enrollment Period from January 1 through March 31 allows one switch to another Medicare Advantage plan or back to Original Medicare. If you are not in Medicare Advantage, you may need a Special Enrollment Period, which requires a qualifying event, or you may have to wait for the next fall.

If you think you were misled about a plan, for example you were told your doctor was in network and later learned otherwise, document what you were told, when, and by whom. You can contact the plan, call 1-800-MEDICARE, or contact your state’s counseling program. In Ohio, that is OSHIIP, which is free. Some situations may qualify for a Special Enrollment Period, and Medicare staff can tell you whether yours does. Do not assume you are stuck.

If your card never arrives or coverage did not start on time, contact the plan first, then 1-800-MEDICARE if it is not resolved, and keep your confirmation number handy.

Frequently Asked Questions

Do I have to do anything during Medicare open enrollment?

No. If your plan is still offered next year and still meets your needs, you can leave it alone and it generally renews. The review is optional, but plans change every year, so it is worth checking at least once.

What is the deadline for Medicare open enrollment?

The window closes December 7. Medicare.gov says the plan must receive your request by that date, so allow some cushion rather than waiting for the last day.

Can I change Medigap plans during the Annual Enrollment Period?

Not as a right. Medigap sits outside the fall window, and in most states an insurer can ask health questions after your Medigap open enrollment period ends. Check the rules for your state and situation first.

Can I make more than one change during open enrollment?

Yes. You can make changes through December 7, and generally the last one you make before the window closes is the one that takes effect on January 1.

What if I miss the Annual Enrollment Period?

If you are on a Medicare Advantage plan, you may be able to switch during the January 1 through March 31 Medicare Advantage Open Enrollment Period. Otherwise you generally need a qualifying Special Enrollment Period, or you wait until next fall.