Medicare’s annual Open Enrollment Period begins October 15 and runs through December 7, the single stretch each year when enrollees can join, switch, or drop a Medicare Advantage or Part D plan for coverage starting January 1, according to CMS Product No. 11219, the fact sheet Medicare updated in March 2026. That window is not the only door: a member whose Medicare Advantage, Part D, or Medicare Cost Plan contract is not renewed for the coming year gets a separate special enrollment period that opens December 8 and runs through the last day of February. The two calendars run independently, and confusing them can leave a household without coverage.
The Annual Election Period’s Rules Under CMS Regulation
The October 15 to December 7 period is formally called the Annual Election Period, and it is open to every Medicare beneficiary regardless of which plan appears on their Medicare card. During those seven weeks a person can enroll in a Medicare Advantage plan, disenroll from one, add or drop Part D drug coverage, or move between Original Medicare and a Medicare Advantage plan in either direction. Every change made during this period takes effect on the same date, January 1 of the following year, which is why insurers mail renewal and cost notices to current members before the window opens.
CMS spells out exactly which changes are permitted during this period in CMS Product No. 11219, the federal fact sheet the agency last updated in March 2026: enrollment into a plan, disenrollment from a plan, and nothing else outside those two categories. The same document lists five other named windows a beneficiary might qualify for instead, including the Initial Enrollment Period tied to turning 65 and special enrollment periods triggered by a move, a lost employer plan, or an institution stay, each running on its own start and end dates rather than the October calendar.
The rules behind that October 15 start date are not just administrative habit; they are written into federal regulation. CMS’s Medicare Advantage and Part D Enrollment and Disenrollment Guidance, most recently updated August 25, 2026, cites 42 CFR §§ 422.62(a)(2)(iii), 422.106(c), and 423.38(b)(3) as the authority for the period and notes that plans may begin marketing next year’s benefits on October 1 but cannot accept, solicit, or process any enrollment request before October 15 itself, even an unsolicited paper form that arrives early.
Inside the decision kit: A cost calculator spreadsheet comparing plans on cost, drugs and doctors, a prescription-by-plan comparison, a provider call script and the Open Enrollment calendar. Open The 2027 Medicare Open Enrollment Decision Kit.
The Non-Renewal Window Runs December 8 Through the End of February
A non-renewal is different from a voluntary switch: it happens when CMS, the insurer, or the drug plan sponsor decides not to continue a contract into the next year, effective January 1, rather than when a member chooses to leave. For a member whose plan is dropped this way, the enrollment guidance sets the special enrollment period to begin December 8 of the current year and end on the last day of the following February, roughly ten weeks longer than the general Annual Election Period. Effective dates inside that window are staggered: a request filed December 8 through December 31 takes effect January 1, a request filed in January takes effect February 1, and a request filed in February takes effect March 1.
A member who lets that window close without picking a new plan does not stay covered by default — they are enrolled in Original Medicare, which carries no prescription drug benefit unless a separate Part D plan is chosen. Medicare’s own enrollment-periods fact sheet warns that a gap of 63 or more days without Medicare drug coverage or other creditable coverage triggers a late enrollment penalty added permanently to the Part D premium, meaning a member who is dropped in December and delays into spring risks a penalty that follows them for as long as they carry Part D coverage.
The non-renewal window is generous specifically because losing a plan is involuntary — a member did nothing wrong and had no advance choice in the matter, so the ten extra weeks give time to compare replacement options before drug coverage or provider networks change without notice. That generosity does not extend to every plan-ending scenario, though; several other special enrollment periods tied to a terminated or modified contract run on much shorter clocks than the one triggered by a straightforward non-renewal.
Contract-Termination Windows Run on Tighter Clocks Than a Non-Renewal
When CMS itself terminates a plan’s contract for cause, the special enrollment period is shorter and centered differently: it begins one month before the termination’s effective date and ends two months after it, rather than the roughly ten-week window that follows a routine non-renewal. A member who does not choose a replacement plan before the termination date is defaulted to Original Medicare on that date, but the special enrollment period stays open for two more months if the member later decides to elect a new Medicare Advantage plan instead.
A plan that ends its own contract voluntarily, or ends it by mutual agreement with CMS during the contract year, triggers yet another timeline: the special enrollment period runs from two months before the termination date through one month after it. A Part D sponsor whose contract terminates for cause on April 30, for example, gives affected members a window running from March 1 through May 31 to pick a replacement, with the new plan’s effective date never earlier than the date it actually receives the enrollment request.
None of these windows should be confused with the Medicare Advantage Open Enrollment Period, which runs every January 1 through March 31 for anyone already in a Medicare Advantage plan and allows exactly one change: switching to a different Medicare Advantage plan, or dropping Medicare Advantage entirely to return to Original Medicare and pick up a standalone drug plan. A member in Original Medicare cannot use this period to join a Medicare Advantage plan for the first time, and a member cannot use it to swap one standalone Part D plan for another.
All of these deadlines sit inside the same regulatory framework CMS maintains on its Medicare Managed Care Eligibility and Enrollment page, which the agency updated on August 25, 2026 to fold in the newest enrollment and disenrollment guidance and which lists six distinct types of election periods governing when a Medicare Advantage or Part D member can act. For a member whose plan is dropped, the practical takeaway sits in that list: the non-renewal special enrollment period, running December 8 through the last day of February, is the one built specifically for a plan a person did not choose to leave.
Comparing Plans Before December 7
None of the enrollment windows described above tell a member how to actually compare what a new Medicare Advantage or Part D plan will cost against the one that was just discontinued. The special enrollment period gives the time to act, but it does not supply the prescription list, provider directory, or premium math a household needs before December 7 or before the last day of February. That gap is where a structured comparison tool becomes the difference between a rushed guess and an informed switch.
The 2027 Medicare Open Enrollment Decision Kit is a 42-page decision kit built around a cost calculator spreadsheet that compares plans on cost, drugs and doctors.
Look up the prescription-by-plan comparison in The 2027 Medicare Open Enrollment Decision Kit.
This article was researched and drafted with the assistance of AI and reviewed by The Money Overview editorial team.
