The Open Enrollment Period Explained: A 2026 Guide for Seniors

Every year, the seven-week window from October 15 to December 7 is the busiest stretch on a Medicare advisor's calendar. It's the Open Enrollment Period — the federal window when most plan changes for the following calendar year are made. This is the version of “what to do during Open Enrollment” that we wish more families had read in September instead of November.

What Open Enrollment actually is, and what year it affects

Open Enrollment runs October 15 through December 7 of each year. Changes made during Open Enrollment take effect January 1 of the following year. So an Open Enrollment decision made in November 2026 changes coverage starting January 1, 2027.

It is the main annual window for switching Medicare Advantage plans, switching Part D prescription drug plans, dropping Advantage to return to Original Medicare, or adding Part D to Original Medicare for the first time. It is not the only window — but for most of these moves, it is the one window that's guaranteed.

What you can do during Open Enrollment

• Switch from Original Medicare to a Medicare Advantage plan.
• Switch from a Medicare Advantage plan back to Original Medicare.
• Switch from one Medicare Advantage plan to another.
• Join, drop, or switch a stand-alone Part D prescription drug plan.

The change becomes effective on January 1. If multiple changes are made during Open Enrollment, the last enrollment received before December 7 is the one that takes effect.

What Open Enrollment does not cover

Open Enrollment does not give you new rights to buy a Medicare Supplement (Medigap) policy. Medigap has its own rules — a guaranteed-issue open enrollment window at age 65 when first signing up for Part B, plus state-specific protections that vary widely. If the goal is to switch from Medicare Advantage to Original Medicare plus a Medigap policy, the Advantage move can happen during Open Enrollment, but the Medigap carrier may still medically underwrite. That's a conversation to have before December 7, not after.

There is a second window, the Medicare Advantage Open Enrollment Period, that runs January 1 through March 31. During that window, someone already enrolled in a Medicare Advantage plan can switch to a different Advantage plan or drop back to Original Medicare with Part D. It's a one-time-per-year window inside that period, and people who only have Original Medicare cannot use it to enroll in an Advantage plan.

Three things to do before October 15

The mistake families make most often is treating Open Enrollment as a research period. By the time the brochures arrive in October, the most important work is already done if it's done right. Three things help most:

1. Find the Annual Notice of Change (ANOC) the current plan mailed in late September. Read the section on premium changes, formulary changes (medications added or removed), and network changes (providers added or dropped). About a third of plan changes year-to-year are meaningful enough to trigger a switch.
2. Make an up-to-date medication list, with dosages and pharmacies. The single biggest source of “this plan looked great in October but isn't working in February” is a medication that wasn't on the formulary anymore — or moved to a higher tier.
3. Make an up-to-date provider list, including primary care, specialists seen at least twice a year, the preferred pharmacy, and any expected upcoming procedures.

A licensed advisor can run the medication list and provider list against every plan available in the area and rank them by total annual cost in a few minutes — but only with that information in front of them.

What a real plan comparison includes

• The plan's premium for the year.
• Each medication's copay and tier, across the full year, including any deductible and donut-hole math.
• Provider network match for every doctor in the patient's care.
• Pharmacy preferences. A “preferred” pharmacy often costs noticeably less than a “standard” one.
• The plan's maximum out-of-pocket limit.
• Star Ratings — the CMS quality score, which moved meaningfully for several carriers in the 2026 plan year.

What a real comparison should not include is “this plan has the cheapest premium, so let's go with that.” Premium is often the smallest line item in the total cost.

Common Open Enrollment mistakes

Three patterns we see every year:

• Switching plans because of a TV ad. The carriers that buy the most TV time do not necessarily offer the best plan in any one ZIP code. The plan that fits the patient is the one that covers their doctors and drugs at the lowest total cost.
• Waiting until the first week of December. The closer to the deadline, the harder it is to get a real conversation. By December 5, advisors are triaging.
• Assuming “if I don't act, nothing changes.” Mostly true — but if the current plan is no longer being offered, or has changed its formulary in a way that drops a medication, the patient may be auto-enrolled into a different plan or default into a coverage gap.

How plans change year to year (and why a quiet October is not a safe October)

Plans are not static. Every year carriers file updated benefit designs with CMS, and even when the headline name stays the same, the details underneath move. Specific changes we see almost every year, across most regions:

• Formulary changes. A medication that was tier 2 can move to tier 3 or tier 4. A drug that was preferred can be replaced by a generic equivalent. Step-therapy rules can be added for a drug that previously had none. For seniors on five or more medications, the odds of at least one of these changing every year are high.
• Network changes. Health systems and large physician groups negotiate annually with carriers. A plan that included the patient's cardiologist this year may not next year — and notifications of those changes often arrive late.
• Premium and copay adjustments. Per-day inpatient copays, specialist copays, and the maximum out-of-pocket limit frequently change. The plan's headline premium may stay flat while a key copay quietly increases.
• Supplemental benefit shifts. Dental allowances, OTC cards, fitness benefits, and transportation benefits change almost every year. These are often the most heavily marketed parts of the plan, but they're also the easiest to discontinue or reduce.

Inertia is the most expensive choice during Open Enrollment. Staying with a plan that has shifted in unfavorable ways can easily cost thousands of dollars over the next year. Reviewing the ANOC for fifteen minutes is the cheapest insurance against that.

How Open Enrollment works for someone in a nursing home or rehab

Residents of skilled nursing facilities and long-term care facilities are in a different situation than the general Open Enrollment population. Long-term care residents have ongoing Special Enrollment Period rights — they can change Medicare Advantage and Part D plans once each month, every month they live in the facility, rather than waiting for Open Enrollment. For short-term rehab stays, the situation depends on length and discharge plans.

For family members helping a parent in a facility during Open Enrollment: the decision is rarely just about the plan. It's about which providers will be in network when the patient discharges, whether home health agencies the facility partners with are in network, whether the post-discharge medication list will be covered, and whether the local pharmacy is preferred. These details can be worked through, but they take time. Starting the conversation in October, not December, is the difference between a calm decision and a rushed one.

A working calendar for the months around Open Enrollment

Treating Open Enrollment as a single date on the calendar — December 7 — is the most common reason families end up rushed. A more useful frame is the eleven-week stretch on either side of the window. Here is what a careful month-by-month preparation looks like.

• Late September: The Annual Notice of Change (ANOC) arrives from the current carrier. Read it. Flag any premium changes, formulary changes, or network changes. Pull the patient's medication list and provider list up to date.
• October 1 – October 14: CMS allows plans to begin marketing for the coming plan year. Brochures and TV ads start to appear, but enrollment isn't open yet. This is the ideal time to book a comparison appointment.
• October 15 – November 30: Open Enrollment is open. This is the calm-decision window. Most advisors have capacity in mid-to-late October. By mid-November, calendars tighten.
• December 1 – December 7: Triage week. Possible to enroll, but advisors are working through backlogs and a mistake here is harder to fix.
• January 1: New plan effective date. The patient may receive new ID cards from the new carrier in late December or early January. Verify that the first prescription refill of the year is processed correctly under the new plan.
• January 1 – March 31: The Medicare Advantage Open Enrollment Period. A second chance, with narrower rules, for anyone already on an Advantage plan to switch or return to Original Medicare with Part D.

People who shouldn't wait for Open Enrollment

Open Enrollment is the main annual window, but it isn't the only one — and for some situations, waiting is the wrong move. A Special Enrollment Period may already be open, with a clock that doesn't align with the Open Enrollment calendar. The most common scenarios:

• A move. A permanent move out of the current plan's service area opens an SEP that starts the month before the move and runs two months after. It cannot wait for Open Enrollment.
• A loss of other coverage. Losing employer or union coverage (or having a spouse lose theirs and the patient dependent on it) typically opens a 63-day SEP.
• Entering or leaving a long-term care facility. Residents of long-term care have ongoing monthly SEP rights.
• A Medicaid eligibility change. Gaining or losing Medicaid opens an SEP and may make D-SNP options available.
• A plan that terminates. If the carrier ends its contract with CMS in the patient's area, an SEP opens with guaranteed-issue Medigap rights in many situations.

If any of these apply, the right move is usually to act on the SEP immediately, not wait. The SEP timing and the Open Enrollment timing rarely line up neatly.

What an Open Enrollment appointment looks like with us

We see clients by appointment from mid-September through early December. The conversation is typically 30 to 60 minutes. We pull the ANOC for the current plan, run the medication list against every plan available in the area, compare provider networks, and walk through the trade-offs. There is no cost — we're paid by the carriers — and there is never any pressure to switch. If the current plan is still the right plan, that's a perfectly good outcome.

If a family member is helping a parent, bring them. Open Enrollment works better with two pairs of ears.