Medicare Open Enrollment for 2027 coverage runs October 15 to December 7, 2026. Changes you make in that window generally start January 1, 2027, and your new plan has to receive your request by December 7. If your current plan is continuing and you do nothing, it renews on its own.
Doing nothing is allowed. It is also how people wake up in January to a higher drug bill, a doctor who left the network, or a deductible they never saw coming.
This post is about the mistakes that cause those surprises. If you still need a prep checklist before you compare plans, use 2 Weeks Before Medicare Open Enrollment: Your 2027 Prep Checklist. For dates and what you can change, see Medicare Open Enrollment for 2027 coverage.
I’m a researcher who compares plan rules and official Medicare pages for readers. I am not a licensed insurance agent or a doctor. Use this with Medicare Plan Finder and free counseling from your State Health Insurance Assistance Program (SHIP).
One new 2027 mistake to avoid: waiting too long on a plan that has an enrollment cap. See how Medicare Advantage enrollment limits work in 2027.
A common 2027 mistake is trusting a plan directory without calling the doctor. Read how to check a Medicare Advantage provider directory before Dec 7.
Another costly mistake is trusting a caller who says they are from Medicare. Learn the red flags of Medicare Open Enrollment scams this fall.
Mistake 1: Ignoring the Annual Notice of Change
Your Medicare Advantage or Part D plan should have mailed an Annual Notice of Change (ANOC) in September. Medicare’s ANOC page explains that this notice shows how premiums, benefits, and costs change for the coming year.
The ANOC is not junk mail. It is the plan telling you, in writing, what changes on January 1. Skipping it is the shortcut to “I thought nothing changed.”
What to mark with a highlighter:
- Monthly premium for 2027
- Medical and drug deductibles
- Your drugs: still covered, same tier, new prior authorization?
- Doctors, hospital, and pharmacy still in network?
- Medicare Advantage out-of-pocket maximum
- Extras you actually use (dental, vision, hearing, OTC)
For a line-by-line read, use Your Medicare Annual Notice of Change for 2027. If you never got an ANOC, call the member services number on your plan card now—not on December 6.
Mistake 2: Not checking your drugs and pharmacy
Drug lists (formularies) and preferred pharmacies change. A medicine that was tier 2 in 2026 can move to a higher tier, need prior authorization, or leave the list. A “preferred” pharmacy can stop being preferred.
Enter every prescription—name, dose, how often—into Medicare Plan Finder and check the pharmacy you actually use. Sort by estimated yearly cost, not the monthly premium alone. Step-by-step screens live in How to find the best Medicare plan in your area for 2027.
If you take insulin or several brand-name drugs, also skim what is already locked in for 2027 in Medicare Part D 2027 plans, costs, and enrollment and Medicare changes for 2027. The Part D out-of-pocket cap rises to $2,400, and the maximum Part D deductible rises to $700. Your plan can charge less than that deductible, or none.
Mistake 3: Assuming “nothing changed” because you liked last year
Plans are allowed to change costs and networks each year. Liking your 2026 plan is not proof it is still the best 2027 fit.
A quick annual check is enough for many people:
- Read the ANOC.
- Run Plan Finder with your current drug list.
- Confirm two or three doctors and your pharmacy for 2027.
- Compare total estimated yearly cost against one or two alternatives.
If the numbers still look good, staying put is a decision—not a default.
Mistake 4: Confusing Open Enrollment with the Medicare Advantage Open Enrollment Period
People mix up two windows every year.
| Window | Dates (for 2027 coverage) | Who it is for | What you can do |
|---|---|---|---|
| Annual Enrollment Period (AEP / Open Enrollment) | Oct 15 – Dec 7, 2026 | People with Medicare | Join, switch, or drop Advantage or Part D; move between Advantage and Original Medicare |
| Medicare Advantage Open Enrollment Period (MA OEP) | Jan 1 – Mar 31, 2027 | Only if you are already in a Medicare Advantage plan | Switch Advantage plans once, or return to Original Medicare and join a Part D plan |
Medicare lists both on its Joining a plan and Open Enrollment pages. The January–March window is a safety net for Advantage members. It is not a reason to skip the fall review, and it is not a Medigap enrollment period.
Mistake 5: Dropping Medicare Advantage without checking Medigap first
Open Enrollment is not a Medigap open window. Under federal rules, your one six-month Medigap Open Enrollment Period generally starts the first month you have Part B and are 65 or older. Outside that window, an insurer can use medical underwriting unless you have a guaranteed-issue right. Some states add protections.
So if you want to leave Advantage for Original Medicare plus a Medigap policy (Plan G or Plan N, for example), find out whether you can buy Medigap at a price you can live with before you drop Advantage. Medicare’s Medigap pages and a SHIP counselor are the right places to sort that out. Our notes on switching from Medicare Advantage to Original Medicare walk through the trap.
Mistake 6: Missing Extra Help and Medicare Savings Programs
If money is tight, plan shopping without checking Extra Help (Low-Income Subsidy) and Medicare Savings Programs is backwards. Those programs can wipe out or shrink Part D costs and, in some cases, help with Part B premiums.
- Extra Help: How to get Extra Help with Medicare Part D costs
- Savings Programs (QMB, SLMB, QI): Medicare Savings Programs guide
People with Medicaid or Extra Help may also be able to change drug coverage more often than once a year. Ask SHIP how that works for you so you do not “save” a switch for December when you could fix a bad drug fit sooner.
As of October 3, 2026, the 2027 Part B premium and deductible are not announced yet. For budgeting, the 2026 figures are still the official ones: $202.90 monthly Part B premium and $283 Part B deductible for most people. When CMS publishes 2027 amounts, update your budget. Those numbers will not rewrite every Advantage drug list.
Mistake 7: Enrolling from a cold call, a parking-lot flyer, or a rushed pitch
Agents and brokers can help when they put your drugs and doctors into Plan Finder and show you the screen. A cold call that pushes one plan before you have seen alternatives is a red flag.
Build your lists first (see the prep checklist), run Plan Finder yourself or with SHIP, and if you talk to an agent, ask them to show the estimate for your drug list—not a generic premium chart. Keep confirmation numbers and plan IDs. Medicare will not cold-call you to demand personal information or payment to “secure” enrollment.
Mistake 8: Waiting until December 7
December 7 is a hard deadline for the plan to receive your request, not a good day to start comparing. Portals slow down. Phone queues get long. A typo in a drug dose can throw off the estimate.
Aim to finish your comparison in the first few weeks of the window. Leave December for confirmation numbers and a calm double-check—not for discovering your cardiologist left the network.
FAQ
If I am happy with my plan, do I still need to do anything?
You do not have to enroll again if the plan is continuing. Still read the ANOC and spot-check drugs and doctors for 2027.
Can I change Medigap plans during Open Enrollment?
Not under the federal Advantage/Part D Open Enrollment rules. Medigap has its own timing and underwriting rules. Ask SHIP before you drop coverage you may not get back easily.
What if my plan is leaving my area for 2027?
That is a nonrenewal, different from a normal ANOC change. Keep the letter, call SHIP promptly, and use Open Enrollment (plus any special enrollment rights) to pick a new plan.
Bottom line
The expensive mistakes are usually quiet: unread mail, an unchecked drug list, mixed-up calendars, and a switch made under pressure. Read the ANOC, run Plan Finder with real data, call SHIP if anything is unclear, and enroll when the comparison is done—not on December 7.
