The claim and verdict
Claim checked: During Medicare's annual Open Enrollment Period, every beneficiary has a federal right to buy any Medigap policy without medical underwriting.
Verdict: False. The annual October 15–December 7 period applies to Medicare Advantage and Part D choices. Medigap has a separate federal enrollment framework.
The federal Medigap window
Medicare says the main Medigap Open Enrollment Period lasts six months and starts the first month a person has Part B and is 65 or older. During that period, an insurer cannot use medical underwriting to deny the policy or change the price because of health history.
After that period, insurers may deny an application or charge more unless the applicant has a guaranteed-issue right. State law can provide additional protections, so the exact answer can depend on residence.
Switching coverage can expose the difference
A beneficiary may use annual Medicare Open Enrollment to leave Medicare Advantage for Original Medicare, but that change does not automatically create a federal right to buy any Medigap plan. Specific trial rights or loss-of-coverage events may create protection, and the timing can be short.
Before dropping coverage, obtain a written answer about Medigap eligibility and effective dates from the insurer or a State Health Insurance Assistance Program counselor. The annual Medicare window creates plan-changing rights; it is not a blanket Medigap acceptance guarantee.
Sources and further reading
Medicare: Get ready to buy Medigap ↗
Medicare: When can I buy Medigap? ↗