A Medigap applicant during the 6-month open enrollment window gets guaranteed issue: no medical underwriting, no premium surcharge for health history, no denial. A Medigap applicant outside that window, in most states, faces a carrier that can decline them outright. Same person, same plan, different calendar position. That gap in protection is the core fact every Medicare broker needs to be able to explain before the window closes.
Most beneficiaries do not know the window exists until someone tells them. Most find out after it has already closed.
Key Takeaways
- The Medigap OEP starts when the beneficiary is simultaneously age 65 or older AND enrolled in Part B. Enrolling in Part B at 67 due to delayed retirement starts the 6-month clock at 67, not at 65.
- Insurers may apply a 6-month pre-existing condition waiting period during the OEP only if the beneficiary did not have 6 months of prior creditable coverage. With 6 months of prior creditable coverage, the waiting period cannot be imposed.
- Guaranteed issue rights outside the OEP are event-driven and narrow: MA plan termination or exit from service area, employer retiree coverage ending, and Medigap insurer insolvency are the primary triggers.
- Birthday-rule states vary significantly in scope. California allows switching to any plan of equal or lesser value. Some states restrict birthday-rule switches to the same plan level only.
- A beneficiary who purchases a Medigap plan during the OEP or under a guaranteed issue event cannot be rescinded based on health history, even if a condition is discovered after enrollment that predates the application.
When the Medigap open enrollment period begins
The Medigap OEP does not start at age 65. It starts when the beneficiary satisfies two conditions simultaneously: they are age 65 or older, and they are enrolled in Medicare Part B. Both conditions must be true at the same moment.
For a beneficiary who retires at 65 and takes Part B effective September 1, 2026, the Medigap OEP runs from September 1, 2026 through the end of February 2027. That is 6 months to shop, compare, and enroll in a Medigap plan without any carrier reviewing their medical history.
For a beneficiary who delays retirement and stays on employer coverage until age 68, the Medigap OEP starts when they take Part B, not at 65. A 68-year-old who has never enrolled in Part B triggers the Medigap OEP the moment Part B coverage begins. The clock did not run while they had employer coverage; it starts fresh.
The Medicare Initial Enrollment Period guide covers the 7-month window for Part A and Part B enrollment in detail, including the distinction between the IEP and the Medigap OEP, which are separate mechanisms with separate clocks.
What guaranteed issue protects during the window
During the Medigap OEP, federal law requires Medigap insurers licensed in the state to:
- Accept any application from a beneficiary in the OEP window, regardless of health status.
- Charge the same premium they would charge a healthy applicant of the same age in the same rating area.
- Not impose a waiting period for pre-existing conditions, provided the applicant had at least 6 months of creditable coverage immediately before the Medigap OEP began.
If the applicant did not have 6 months of continuous prior creditable coverage, the insurer may impose a pre-existing condition waiting period of up to 6 months. The waiting period can be reduced by the length of any prior creditable coverage that does exist.
Outside the OEP in a non-birthday-rule state, none of those protections apply. A carrier reviewing an application from a 70-year-old with a history of cardiovascular disease, kidney disease, or cancer can decline the application or rate it significantly above standard. The OEP is the one moment when health history is taken off the table.
Guaranteed issue rights outside the OEP
Federal law also creates guaranteed issue rights triggered by qualifying events, independent of the standard 6-month OEP. These rights are more limited in scope but protect beneficiaries who lose coverage involuntarily.
| Qualifying event | Guaranteed issue right | Window |
|---|---|---|
| MA plan leaves service area or terminates contract | Any Medigap plan sold in the state (Plans A, B, C, F, K, L typically) | 63 days from loss of coverage |
| Employer retiree coverage ends involuntarily | Plans A, B, C, F, K, L (varies by state) | 63 days from loss of coverage |
| Medigap insurer becomes insolvent or plan terminated | Comparable Medigap plan from another insurer | 63 days from notice of termination |
| MA plan materially reduces benefits or increases cost-sharing | Plans A, B, C, F, K, L in most states | 63 days from notification of change |
| Medicare SELECT plan's providers leave service area | Original Medicare SELECT plan or comparable non-SELECT plan | 63 days from network change |
Illustrative summary based on federal law. Specific plan availability under guaranteed issue events varies by state. Confirm with the insurer and state insurance department for the applicable plan year.
Birthday-rule states: the annual window
A growing number of states have enacted Medigap birthday rules, which create an annual guaranteed issue window around a beneficiary's birthday. These rules operate outside the standard OEP and outside federal guaranteed issue events. They exist purely under state insurance law and vary considerably in scope.
California's birthday rule is the most permissive. California beneficiaries who have held a Medigap plan for at least one year have a 60-day window after their birthday each year to switch to any Medigap plan with equal or lesser benefits from any carrier, without underwriting. Oregon provides a similar annual window. Illinois enacted a birthday rule that applies after the beneficiary has held their current Medigap plan for a year. Missouri, Nevada, Oklahoma, Louisiana, Idaho, and Maryland have each enacted variations.
The differences matter. Some states allow switching to a plan with higher benefits; others restrict the switch to equal or lesser. Some require 30 days notice; others require 60. A broker working across state lines needs to verify the current birthday-rule status and mechanics for each state, since legislation is updated periodically and the details are not uniform.
States without a birthday rule and without a qualifying event leave beneficiaries outside the OEP with no guaranteed path to Medigap coverage. A 74-year-old who enrolled in a Medicare Advantage plan at 65, never took Original Medicare, and now wants to switch back faces full medical underwriting in most non-birthday-rule states.
What this means for the Medicare enrollment conversation
The Medicare election period discussion and the Medigap enrollment conversation involve different rules and different windows. The Medicare AEP vs OEP vs MA SEP guide covers the MA election periods, which operate separately from Medigap OEP. A broker who understands both sets of rules can explain why telling a client to "look at Medigap during OEP" is a category error: Medicare OEP is an MA election window; Medigap OEP is a one-time 6-month window at Part B enrollment.
The practical conversation sequence: confirm when the client is taking Part B, calculate the Medigap OEP window, and establish whether they want to compare MA plans or Original Medicare plus Medigap before the OEP closes. A client who enrolls in a MA plan at 65 without considering the Medigap OEP may not get another guaranteed issue shot for years unless a qualifying event occurs or a birthday-rule state applies.
Frequently asked questions about Medigap guaranteed issue rights
The questions that come up most often when clients ask about Medigap enrollment timing and what happens if they miss the open enrollment window.
When does the Medigap open enrollment period start and end?
The Medigap open enrollment period begins on the first day of the month in which a beneficiary is both age 65 or older and enrolled in Medicare Part B. It lasts exactly 6 months. A beneficiary who turns 65 in September and enrolls in Part B effective September 1 has a Medigap OEP from September 1 through the end of February. A beneficiary who delays Part B enrollment until age 67 due to employer coverage has a Medigap OEP beginning with their Part B effective date at 67. The 6-month clock does not start at age 65 unless Part B enrollment also begins at 65. Beneficiaries who enroll in a Medicare Advantage plan at 65 rather than Original Medicare may not trigger the Medigap OEP if they are not simultaneously enrolled in Part B as a standalone benefit.
What does guaranteed issue mean for Medigap applicants?
Guaranteed issue during the Medigap OEP means the insurer must accept the application, cannot charge a higher premium based on health status, and cannot impose a waiting period for pre-existing conditions if the applicant had 6 months of creditable coverage immediately before the Medigap OEP began. Outside the OEP, in states without a birthday rule or other guaranteed issue protection, Medigap insurers can decline applications, charge higher premiums for health history, or impose a pre-existing condition waiting period. A beneficiary with a serious chronic condition who misses the guaranteed issue window may find themselves unable to obtain a Medigap plan with comprehensive coverage at standard rates, or declined entirely.
What events trigger guaranteed issue rights outside the open enrollment period?
CMS recognizes a set of qualifying events that grant guaranteed issue rights to beneficiaries outside the standard Medigap OEP. The most common events a broker will encounter are: a Medicare Advantage plan terminating its contract with CMS or leaving the beneficiary's service area, causing involuntary disenrollment; an employer-sponsored retiree health plan ending coverage, if the beneficiary enrolled in the plan at 65 instead of Original Medicare and is now losing that coverage; a Medigap insurer becoming insolvent or having its plan terminated; and the beneficiary returning to Original Medicare after a Medicare SELECT plan's provider network becomes unavailable in the service area. The guaranteed issue right in these cases is typically limited to specific Medigap plan types and has a defined window, often 63 days from the qualifying event. Documentation of the triggering event is required by the carrier.
Which states have Medigap birthday rules and what do they allow?
As of 2026, the states that have enacted some form of a Medigap birthday rule or annual guaranteed issue window include California, Idaho, Illinois, Louisiana, Maryland, Missouri, Nevada, Oklahoma, and Oregon. The specifics vary significantly. California allows a beneficiary to switch to any Medigap plan of equal or lesser benefit during a 60-day window around their birthday each year, without underwriting. Oregon provides a similar window. Illinois enacted a birthday rule applicable to beneficiaries over 65 who have held a Medigap plan for at least one year. The window length, eligible plan types, and whether the beneficiary can switch to a higher-benefit plan differs by state. Other states have proposed birthday-rule legislation in recent sessions. A broker working in multiple states should verify the current rule for each state, as legislation can change. Connecture does not advertise a birthday-rule state tool on its public site as of August 2026.
Can a Medigap insurer rescind coverage after it is issued during the open enrollment period?
A Medigap plan issued during the open enrollment period or under a guaranteed issue event cannot be rescinded based on health conditions, pre-existing diagnoses, or claims that the applicant failed to disclose a condition at the time of application — with one exception. If the applicant made a material misrepresentation on the application with the intent to defraud, rescission may be available under state insurance law, subject to state-specific procedural requirements. The federal Medigap guarantee does not protect deliberately false statements. For an applicant who disclosed all conditions truthfully or who is in a guaranteed issue situation where health questions were not asked, the coverage is protected against health-based rescission after a 2-year contestability period in most states, which mirrors standard life and disability insurance practice. A beneficiary who receives a rescission notice should immediately contact their state insurance commissioner.
