The Enrollment Window Opening October 15 Does Not Cover Medigap. That One Lasts Six Months and Never Repeats.

Medicare's annual enrollment period opens on October 15 and closes on December 7. It is the window for switching Medicare Advantage plans, changing Part D drug coverage, or moving between Original Medicare and an Advantage plan. It is not a window for buying a Medigap policy. Medigap, the private insurance that covers some of Original Medicare's out-of-pocket costs, runs on a separate clock that most people pass through once and never see again.

The six-month window

According to the CMS guide Choosing a Medigap Policy, the Medigap open enrollment period lasts six months and starts the first day of the month in which a person is 65 or older and enrolled in Medicare Part B. Part B enrolment has to come first; a Medigap policy cannot be bought without it. The period is one-time. It does not come round again each autumn.

What the window buys is protection from medical underwriting. Inside it, an insurer must sell any Medigap policy it offers in that state, and cannot refuse coverage or charge more because of past or present health problems. Medicare.gov states the position outside the window plainly: there is no federal guarantee that an insurance company will sell you a Medigap policy, and if one will, it may cost more because of health history.

Pre-existing conditions, and the look-back

Even inside the open enrollment period, an insurer may impose a waiting period of up to six months before covering costs related to a pre-existing condition. Conditions can only be excluded if they were treated or diagnosed in the six months before coverage starts, which the guide calls the look-back period. Prior creditable coverage shortens or eliminates that wait where the break in coverage was 63 days or less; with at least six months of continuous creditable coverage, there is no wait at all. Policies issued since 1992 are guaranteed renewable.

Guaranteed issue rights, and the 63-day rule

Outside the six-month window, federal law still creates specific situations in which an insurer must sell. The deadlines are tight and repeat across most of them: apply up to 60 days before coverage ends, or no more than 63 days after it ends. The guide lists the main circumstances.

• A Medicare Advantage plan leaves Medicare, stops serving the area, the member moves out of its service area, or its network changes significantly. The switch is to Original Medicare only.
• Employer, union, retiree or COBRA coverage ends. The 63-day clock runs from the latest of the coverage end date, the notice date, or a claim denial date.
• A Medicare SELECT policy holder moves out of its service area.
• A Medicare Advantage or PACE trial right, for someone who joined at 65 within their first year of eligibility. Rights may extend 12 months in some cases.
• A Medigap policy was dropped to join a Medicare Advantage plan, less than a year has passed, and the member wants it back. The former policy is only available if the same insurer still sells it.
• The Medigap insurer goes bankrupt, or coverage ends through no fault of the policyholder.
• The Medicare Advantage plan or insurer broke rules or misled the member.

Where more than one situation applies, the guide says a person may choose the one that works best for them. Some states provide additional rights beyond these.

Which plans still exist

Medigap policies are standardised and lettered. Plans C and F are not available to anyone who became newly eligible for Medicare on or after January 1, 2020; those eligible before that date who have not yet enrolled may still buy them. Plans D and G provide the same benefits as C and F respectively, minus coverage of the Part B deductible. Plans E, H, I and J are no longer sold, though existing policies can generally be kept.

High-deductible versions of F and G exist in some states. For 2026, the guide puts the high-deductible amount at $2,950 in deductibles, copayments and coinsurance before the policy pays, plus a separate $250 annual deductible for foreign travel emergency care. The guide lists the 2026 Part B deductible as $202.90.

Three states do it differently

Massachusetts, Minnesota and Wisconsin use their own standardised designs rather than the lettered plans. Massachusetts offers Core, Supplement 1 and Supplement 1A. Minnesota offers Basic and Extended Basic plans with riders. Wisconsin offers one Basic Plan with optional riders, 50 percent and 25 percent cost-sharing plans, and a high-deductible option set at $2,950 for 2026. The guide also lists 33 states that require insurers to offer at least one Medigap policy to people under 65, though some limit that to people with disabilities or end-stage renal disease.

What Medigap does not do

Medigap covers some Original Medicare cost-sharing, including copayments, coinsurance and deductibles, and some plans cover foreign travel emergencies. It generally does not cover long-term care, vision or dental care, hearing aids, glasses or private-duty nursing. Policies sold after 2005 do not include drug coverage; Part D is separate. A Medigap policy cannot be bought while enrolled in a Medicare Advantage plan, except when switching back to Original Medicare, and a Medigap policy kept while in an Advantage plan will not pay that plan's deductibles, copayments, coinsurance or premiums.

The practical consequence of the two separate calendars is that the decision many people face in the October-to-December window is narrower than it looks. Advantage and Part D choices reset annually. The Medigap decision, for most people, was made once at 65 and is far harder to revisit.