Medicare Supplement

Does Your Medicare Eligibility Date Limit Your Medigap?

BOISE — If you have a Medigap policy in the Treasure Valley — or you are thinking about buying one — a handful of moving pieces reset every year, and 2026 is no exception. The plan letters you can even shop for depend on when you first became eligible for Medicare. The Part B deductible that sits underneath Plans G and N gets a new number for the calendar year. And insurers refile their rates with the Idaho Department of Insurance on their own schedule, so the price of the same lettered plan can shift while the benefits stay identical.

Here is what Boise readers should keep in mind heading into the new year.

What "plan-letter eligibility" actually means

Medigap policies are sold by letter — A, B, D, G, N, and so on — and each letter is standardized by federal law. That means the benefits inside a Plan G are the same at every insurer that sells one.

The catch is that not every letter is available to every shopper. People who became eligible for Medicare before January 1, 2020 can still buy Plans C and F, because those plans cover the Part B deductible. People who became eligible on or after January 1, 2020 cannot buy C or F as new policies — the letters available to them are A, B, D, G, G-HD, K, L, M and N.

If you already own a Plan C or Plan F from before that cutoff, you can keep it. The rule only affects new purchases.

The Part B deductible reset — why it matters for Plans G and N

Plans G and N are popular precisely because they leave the Part B deductible for the member to pay, and then cover the rest of the standard gaps. Every January, that Part B deductible number resets to whatever CMS has set for the new calendar year. The 2026 figure is posted on medicare.gov under Medicare costs.

Nothing about the plan design changes when the deductible resets — you simply meet the new year's amount before Part B cost-sharing kicks in. If you own a Plan G-HD (high-deductible G), your plan deductible is separate and is also set federally.

Rate-adjustment season in Idaho

Medigap premiums are not set by Medicare. Insurers file proposed rates with the Idaho Department of Insurance, and those filings are what drive the renewal letters you see in the mail. Rates can be based on your age at issue, your attained age, or a community rate — the method depends on the insurer and the policy form.

Because Medigap benefits are standardized, the same lettered plan from two different insurers covers the same things. What differs is:

• The premium and how it is calculated
• Whether you would face medical underwriting to switch
• Household discounts, if any
• Customer service and claims handling

If your renewal notice arrives and the number surprises you, you can look up the carrier's filing at the Department of Insurance or call Idaho SHIBA (the State Health Insurance Benefits Advisors program) for free, unbiased help.

Who sells Medigap in the Boise area

Boise is in Ada County. In ZIP 83702, the Medicare.gov Medigap search listed 16 insurers offering Plans A, B, C, D, F, F-HD, G, G-HD, K, L and N across the group. The full table below shows every insurer and the letters each one files in Idaho. A few notes on what the roster tells you:

• Plan G and Plan N are the two letters most widely offered across Idaho carriers.
• High-deductible G (G-HD) is filed by several insurers, giving newly eligible shoppers a lower-premium option that trades a higher out-of-pocket exposure.
• Plans C and F still appear in the roster because carriers continue to serve members who were eligible before 2020.

If you want to compare insurers, use the Medicare.gov Medigap policy search with your ZIP code — it shows the plans filed for your area in real time.

Switching plans: the underwriting question

One rule that trips people up: outside your six-month Medigap Open Enrollment Period (which starts when you are 65 and enrolled in Part B), insurers in Idaho can generally use medical underwriting when you apply to switch. That means your health history can affect whether you are accepted and what you pay.

There are limited "guaranteed issue" situations — for example, if a plan you rely on ends coverage in your area, or you lose other coverage through no fault of your own. If you think one of those might apply to you, confirm it with Idaho SHIBA before you drop what you have.