4.1 Medigap (Medicare Supplement) Basics & Guaranteed Issue Rights

Why This Topic Matters

Medigap questions sit inside Module 1 (Medicare Basics, 20% of the exam), but they are some of the highest-stakes questions on the whole test because they intersect with Module 4's marketing rules. An agent who misunderstands Medigap can accidentally commit a compliance violation — for example, selling a Medigap policy to a client already enrolled in a Medicare Advantage (MA) plan without properly disenrolling them, or telling a client a Medigap plan "covers everything" when it never covers prescription drugs. AHIP exam writers love scenario questions that test whether you know which enrollment window applies and which products can legally be combined, so expect several questions built around a beneficiary's exact situation and timeline.

What a Medigap Policy Actually Is

A Medigap (Medicare Supplement) policy is a privately sold insurance product, regulated under federal and state law, that pays some or all of the cost-sharing gaps left by Original Medicare — deductibles, coinsurance, and copayments under Parts A and B. Medigap policies are standardized: in every state except Massachusetts, Minnesota, and Wisconsin (which use their own systems), each lettered plan (A, B, D, G, K, L, M, N, plus C and F for those grandfathered in) must offer identical benefits no matter which insurance company sells it. Only the premium, customer service, and financial strength of the carrier differ between two companies selling the same lettered plan.

A Medigap policy works only alongside Original Medicare. It cannot be paired with a Medicare Advantage plan, and federal law prohibits selling a new Medigap policy to someone the agent knows is currently enrolled in an MA plan, unless the sale is timed to coincide with the beneficiary disenrolling from MA and returning to Original Medicare.

The 2010 Standardization and the 2020 MACRA Cutoff

Two regulatory changes show up constantly on the exam:

1. 2010 (Medicare Improvements for Patients and Providers Act, MIPPA): Plans E, H, I, and J were discontinued for new sales, and Plans M and N were introduced. This produced the current 10-plan standardized lineup (A, B, C, D, F, G, K, L, M, N).
2. January 1, 2020 (Medicare Access and CHIP Reauthorization Act, MACRA): Plans C, F, and High-Deductible F were closed to anyone newly eligible for Medicare on or after that date because they cover the Part B deductible, which Congress decided created first-dollar coverage that discouraged cost-conscious care. Beneficiaries who were already eligible for Medicare before 2020 can keep or still buy Plan C or F; anyone newly eligible on or after January 1, 2020 cannot.

Because Plan F is closing off to new entrants, Plan G (and High-Deductible G) is now the most comprehensive plan available to newly eligible beneficiaries — it covers everything Plan F does except the annual Part B deductible ($283 in 2026), which the beneficiary pays out of pocket before Plan G benefits begin.

The Medigap Open Enrollment Period

The single most-tested Medigap concept is the Medigap Open Enrollment Period (OEP) — a one-time, 6-month window that starts the first day of the month in which a person is both age 65 or older and enrolled in Part B. During this window, an insurer must sell any Medigap policy it offers, at the best available rate, regardless of health history — no medical underwriting, no pre-existing condition exclusion.

Common exam trap: Do not confuse this with the Medicare Advantage Open Enrollment Period (MA OEP, January 1–March 31 every year) or the Annual Enrollment Period (AEP, October 15–December 7). All three use the word "enrollment," but the Medigap OEP happens only once, is tied to turning 65 and having Part B, and has nothing to do with switching MA plans.

Guaranteed Issue Rights Outside the OEP

Outside the one-time OEP, an insurer can generally medically underwrite a Medigap application — asking health questions and denying coverage or charging more based on the answers. However, federal law creates guaranteed issue (GI) rights in specific situations that force an insurer to sell a Medigap policy (usually Plan A, B, C, F, K, or L, depending on the state) without underwriting. The most tested GI triggers are:

• Trial right: A beneficiary who enrolls in an MA plan for the first time at 65 and disenrolls within 12 months has a right to buy a Medigap policy as if returning from Original Medicare for the first time.
• Involuntary loss of coverage: The MA plan or Medigap insurer leaves the area, becomes insolvent, commits fraud, or otherwise ends coverage through no fault of the beneficiary.
• Move out of the plan's service area.

Each GI right comes with a strict application window, typically 63 days from the date coverage ends or the beneficiary is notified. Missing that window can mean losing the guaranteed issue right entirely and facing full medical underwriting.

Scenario

Mrs. Ito turns 65 and enrolls in Part B in April 2026. Her Medigap OEP runs April 1 – September 30, 2026. If she applies for Plan G in July, the insurer must issue the policy regardless of her health history. If she instead waits until November 2026 to apply — outside her OEP and without a qualifying GI event — the insurer may ask health questions and can deny her or charge a higher premium.