16.3 Medicare Supplement (Medigap) Standardized Plans and Enrollment
Key Takeaways
- Medigap supplements Original Medicare's gaps and requires both Part A and Part B; it cannot be paired with Medicare Advantage.
- Plans are federally standardized by letter (A, B, C, D, F, G, K, L, M, N) — the same letter means identical benefits across all insurers, so only price and service differ.
- Only Plans C and F cover the Part B deductible, and both are closed to anyone newly eligible for Medicare on or after January 1, 2020; Plan G is the top option for new enrollees.
- The 6-month Medigap Open Enrollment Period (starting when 65+ and on Part B) grants a guaranteed-issue right with no medical underwriting.
- Producers must deliver the CMS Guide and Outline of Coverage; selling duplicate Medigap, selling to MA enrollees, and twisting are prohibited.
Medicare Supplement (Medigap) Standardized Plans and Enrollment
A Medicare Supplement policy, commonly called Medigap, is private insurance that pays some or all of the out-of-pocket costs left by Original Medicare — the Part A and Part B deductibles, coinsurance, and copayments. Medigap only works with Original Medicare; it does not coordinate with Medicare Advantage. To buy one, the applicant must have both Part A and Part B.
Standardization: the lettered plans
Under federal law, Medigap plans are standardized into lettered plans A, B, C, D, F, G, K, L, M, and N. 'Standardized' means Plan G from one insurer covers the exact same benefits as Plan G from any other insurer — only the premium and service differ. This is the heart of the topic: the exam tests that benefits are identical across companies for the same letter, so comparison shopping is purely about price and reliability.
Core benefit comparison (the most-tested rows):
| Benefit | Plan G | Plan N | Plan K |
|---|---|---|---|
| Part A coinsurance + 365 extra hospital days | 100% | 100% | 100% |
| Part B coinsurance | 100% | 100% (small office/ER copays) | 50% |
| Part A deductible | 100% | 100% | 50% |
| Part B deductible | Not covered | Not covered | Not covered |
| Out-of-pocket limit | None needed | None needed | Annual limit applies |
Trap: Plans C and F are the only plans that cover the Part B deductible, and they are closed to anyone newly eligible for Medicare on or after January 1, 2020.
The Plan F / Plan G shift
Because first-dollar coverage was discouraged, Plan F (and high-deductible F) and Plan C are no longer sold to newly eligible beneficiaries after January 1, 2020. People already eligible before that date may keep or still buy them. As a result, Plan G has become the most comprehensive plan available to new enrollees — it mirrors Plan F except the enrollee must pay the Part B deductible themselves. Expect a question that hinges on this date.
Cost-sharing plans K and L
Plans K and L cover a percentage of gaps (K = 50%, L = 75%) but include an annual out-of-pocket limit; once the enrollee hits it, the plan pays 100% for the rest of the year. They trade lower premiums for more cost-sharing — useful for budget-conscious clients who want catastrophic protection. Plan N pays Part B coinsurance fully except for small copays (up to ~$20 office, ~$50 ER).
The Medigap Open Enrollment Period
The single most important consumer protection is the Medigap Open Enrollment Period (OEP): a 6-month window that begins the first month the person is both age 65 or older and enrolled in Part B. During this window the applicant has a guaranteed-issue right — the insurer cannot medically underwrite, deny coverage, or charge more for health reasons, even with pre-existing conditions. Miss this window and, outside guaranteed-issue situations, the insurer may underwrite.
Guaranteed-issue (trial) rights
Beyond the OEP, federal guaranteed-issue rights arise in specific situations — for example, when a beneficiary's MA plan leaves the area, or during the 'trial right': someone who joins a Medicare Advantage plan when first eligible and disenrolls within 12 months can return to Original Medicare and buy a Medigap policy without underwriting. These protections prevent enrollees from being trapped by a one-time MA choice.
Required disclosures and prohibited practices
Producers must deliver the 'Guide to Health Insurance for People with Medicare' (the CMS outline of coverage) and an Outline of Coverage at or before application. Prohibited acts the exam tests: selling a duplicate Medigap policy to someone who already has one, selling Medigap to an MA enrollee, twisting/churning replacements, and high-pressure cold-call tactics. Replacement requires a signed replacement notice and a comparison of old vs. new coverage.
Worked enrollment scenario
Lin turns 65 on June 10 and enrolls in Part B effective June 1. Her Medigap OEP runs June 1 through November 30 — six months. If she applies for Plan G on August 1, the insurer must issue the policy regardless of her diabetes, at the same rate as a healthy applicant. If she instead waits until the following March, she is outside the OEP, has no guaranteed-issue event, and the insurer may underwrite and decline or surcharge her — a costly delay the exam rewards you for spotting.
A client newly eligible for Medicare in 2026 wants a Medigap plan that covers the Part B deductible. Which is true?
During the 6-month Medigap Open Enrollment Period, what protection does an applicant have?