Medicare Open Enrollment 2027: Key Dates, New Rules, and How to Actually Compare Plans

Medicare’s Annual Enrollment Period for 2027 coverage runs October 15 through December 7, 2026 — the annual window when you can switch Medicare Advantage plans, change Part D drug coverage, or move between Original Medicare and Medicare Advantage.

This year’s window comes with more than the usual “review your plan” advice. A rule change around provider network departures, looser marketing restrictions, and a newly permanent Part D benefit structure all make 2027’s open enrollment worth more than a five-minute glance at your renewal notice.

Here’s what’s actually different, what to watch for, and where people most often get tripped up.

The Basics: What Open Enrollment Actually Lets You Do

During AEP, you can switch from Original Medicare to a Medicare Advantage plan, switch back from Medicare Advantage to Original Medicare, move from one Medicare Advantage plan to another, or change your standalone Part D prescription drug plan. Any change you make takes effect January 1, 2027.

If you do nothing, your current coverage generally continues automatically — but “automatically continues” doesn’t mean “stays the same.” Premiums, deductibles, drug formularies, and provider networks can all change from one year to the next even without you lifting a finger, which is exactly why CMS and consumer advocates keep telling people to review their coverage every fall rather than assuming last year’s plan is still the best fit.

What’s New for 2027

CMS finalized a rule eliminating the “significance” threshold that used to apply to provider network departures. Previously, losing access to your doctor only triggered a Special Enrollment Period if the departure was considered a “significant” change to your plan’s network — a standard that left a lot of individual departures uncovered. Under the new rule, if your specific doctor leaves your plan’s network, that alone can qualify you for a Special Enrollment Period to find a new plan, regardless of how many other providers stayed.

Marketing restrictions on insurers, agents, and third-party marketing organizations also loosen starting October 1, 2026. Consumer advocates expect this to translate into a noticeably heavier volume of mail, phone calls, and advertising during this year’s AEP — worth knowing in advance so an unfamiliar call doesn’t catch you off guard.

On the drug coverage side, the Part D redesign’s $2,400 annual out-of-pocket cap — first introduced as part of a multi-year phase-in — becomes a permanent, ongoing feature of the program for 2027, not a temporary provision. For the fuller picture on where 2026 Medicare costs and premiums stand heading into this transition, see my 2026 Medicare coverage changes guide.

Subscribe or follow us and I’ll update this page as CMS finalizes any additional 2027 plan details before AEP opens.

The Confusion That Costs People the Most: AEP vs. Medigap Open Enrollment

This is the single biggest point of confusion I see, and it can be an expensive one. Medicare’s Annual Enrollment Period (Oct 15–Dec 7) and Medigap Open Enrollment are two completely different things, governed by different rules.

Medigap Open Enrollment is a one-time, 6-month window that starts the month your Medicare Part B coverage begins — not the month you turn 65, and not every fall. During that window, insurers must sell you any Medigap policy they offer at the standard rate, with no health questions and no denial for pre-existing conditions.

Once that window closes, most states allow insurers to use medical underwriting, meaning they can charge you more, exclude pre-existing conditions, or deny you coverage outright based on your health.

That distinction matters a lot if you’re considering switching from a Medicare Advantage plan back to Original Medicare plus a Medigap policy during this fall’s AEP. You can generally make that switch during AEP without issue on the Medicare Advantage side — but picking up a new Medigap policy outside your original 6-month window can trigger medical underwriting in most states, meaning a health condition could result in a higher premium or an outright denial.

A handful of states (including California, New York, and Connecticut) offer additional guaranteed-issue protections, but they’re the exception, not the rule.

Example — Robert, 68, has had a Medicare Advantage plan since he turned 65. During this year’s AEP, several of his specialists left his plan’s network, and under the new rule, that alone qualifies him for a Special Enrollment Period. He wants to switch to Original Medicare plus a Medigap plan, but because his one-time 6-month Medigap window closed three years ago, he’ll likely face medical underwriting for a new Medigap policy — something he didn’t realize until he started shopping.

Example — Linda, 66, is happy with her current Part D plan but decides to check anyway during AEP. Her plan’s formulary changed for 2027, moving one of her regular medications to a higher cost tier — a shift that would have cost her several hundred dollars over the year if she hadn’t compared options and switched to a plan that still covers it affordably.

What to Actually Check This Fall

Start with your Annual Notice of Change, which every Medicare Advantage and Part D plan is required to mail by the end of September — it lists exactly what’s changing about your specific plan for 2027. Compare your current plan’s premium, deductible, and total out-of-pocket maximum against at least one or two alternatives using the Medicare Plan Finder at Medicare.gov, since premiums alone don’t tell the whole cost story.

Confirm your doctors and preferred pharmacy are still in-network for whatever plan you choose, and check your specific medications against each plan’s drug formulary rather than assuming coverage carries over. If you’re on a Medicare Advantage plan and considering Original Medicare with a Medigap policy, get clarity on your state’s underwriting rules before assuming the switch will be smooth.

For a broader look at what happens if your specific plan is discontinued rather than just changed, see my guide to Medicare Advantage plan exits for 2027.

If your income is limited, it’s also worth checking whether you qualify for Medicare Extra Help, which can eliminate your Part D deductible and cap copays regardless of which plan you choose during AEP. And since Medicare Part B premiums are usually deducted directly from your Social Security check, it’s worth reviewing my Social Security COLA guide alongside your plan comparison to see how the two numbers interact for 2027.

Common Issues to Watch Out For

I hear the same handful of mix-ups from readers every fall, so here’s what trips people up most.

Assuming AEP and Medigap Open Enrollment are the same window. They’re governed by entirely different rules — AEP is annual and universal, while Medigap Open Enrollment is a one-time 6-month window tied to when your Part B started. Confusing the two can lead to an unpleasant underwriting surprise.

Assuming a new health diagnosis creates extra flexibility. A serious diagnosis during the year doesn’t extend or reopen your Medigap window, and it doesn’t change AEP’s fixed October 15–December 7 dates — special circumstances generally require a qualifying life event (like moving or losing employer coverage), not a change in health status alone.

Ignoring the Annual Notice of Change because “my plan was fine last year.” Formularies, networks, and cost-sharing can all shift year to year even when your premium looks unchanged — the notice is the fastest way to catch a change that affects you specifically.

Not checking whether a network departure now qualifies for a Special Enrollment Period. Under the new rule, an individual doctor leaving your network can be enough on its own — a right that didn’t clearly exist before this rule change, so it’s worth asking your plan directly if you’ve lost access to a provider.

Being caught off guard by increased marketing volume. With marketing restrictions loosening October 1, 2026, expect more calls and mail than in past years — legitimate outreach from your own plan is normal, but never give personal or Medicare information to an unsolicited caller you can’t independently verify.

Looking Ahead: What to Watch After This AEP

A separate window — the Medicare Advantage Open Enrollment Period, running January 1 through March 31, 2027 — gives Medicare Advantage enrollees one additional opportunity to switch plans or return to Original Medicare if their AEP choice doesn’t turn out to work well. It’s more limited than AEP (no switching into Medicare Advantage from Original Medicare during this window), but it’s a real second chance if a new plan’s network or formulary turns out to be a problem once you actually start using it.

I’m also watching how the loosened marketing rules play out in practice this fall — a heavier volume of outreach can make it harder to distinguish legitimate plan communications from aggressive sales tactics, and it’s a dynamic CMS may revisit in future years depending on how the 2027 season goes. I’ll update this page as more 2027 plan specifics become available closer to October 15.

Veterans juggling Medicare alongside VA benefits should also double-check how the two interact — see my VA disability compensation guide for the current payout tables, since VA and Medicare coverage decisions are made independently of each other.