Medigap vs Medicare Advantage 2026: IRMAA, MOOP, Plan G, Deadlines

What the choice does not change: Part B and IRMAA

A retiree with high income pays the income-related monthly adjustment amount on Part B whichever way the rest of the coverage is built. The CMS 2026 fact sheet gives the standard premium of $202.90 and five higher totals by modified adjusted gross income, which the SSA assesses from a return two years back (see our IRMAA brackets page for the look-back, the Part D surcharge and the real estate cases). Medicare.gov says of Medicare Advantage: “You must have Part B and keep paying your Part B premium to stay in your plan.” And of Medigap: “You also have to pay your monthly Medicare Part B premium.” So this block of cost is common to both columns.

Source: CMS “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet (monthly totals and income bands). The two annual columns are our arithmetic: the monthly total times 12, and twice that for two enrolled spouses. Part D surcharges are extra and also apply to a Medicare Advantage plan that includes drug coverage; see the IRMAA page.

Two consequences for a reader at $250,000 or more. First, a premium-free Medicare Advantage plan cannot lower the Part B line: a single filer over $205,000 sits in tier 4 and pays $5,355.60 a year more than the standard premium for Part B alone (our arithmetic: $649.20 less $202.90, times 12). Second, Medicare.gov notes that some plans “may help pay all or part of your Part B premium,” without giving an amount, and we have not verified whether any such reduction changes the IRMAA calculation. If a plan advertises one, ask for the dollar figure in writing.

The tail risk: a limit for Medicare Advantage, a deductible for Plan G

Original Medicare pays most of an inpatient or outpatient bill and leaves the beneficiary 20 percent of Part B services with no yearly stop. The 2026 Part A deductible is $1,736 per benefit period, with $434 a day for hospital days 61 to 90, and Medicare.gov lists Part B coinsurance as “usually 20%” of the Medicare-approved amount. Medigap and Medicare Advantage are the two ways to put a boundary on that.

Source: Medicare.gov “Compare Medigap Plan Benefits” (2026 chart, read from the page markup, whose benefit marks are icons), “Your coverage options” and “Costs”; CMS fact sheet; CMS contract year 2026 MOOP file; KFF, June 2026. Rows marked “our reading” are our interpretation of the chart, not a quotation.

Four details inside the table matter to a high-income buyer. A Plan G is not a cap in the legal sense; it is a coverage design whose cost-sharing, for Medicare-covered services, is the Part B deductible, and it does nothing for services Medicare does not cover. The Medicare Advantage limit, in KFF’s words, applies to “Part A and B services,” not to plan premiums or other benefits. Medigap “only covers one person,” so a couple buys two policies. And for the buyer who expects to use an HSA, Medigap premiums are the one health premium the HSA cannot pay; our HSA and Medicare page lists which premiums qualify.

What the Medicare Advantage ceiling actually is

CMS publishes the limits in a yearly calculation file. For contract year 2026 a plan on the mandatory limit must set an in-network figure between $6,751 and $9,250 and a combined in-network and out-of-network figure between $6,751 and $13,900; the intermediate in-network range ends at $6,750 and the lower at $4,200. For 2027 the mandatory ceiling is $9,850 in-network and $14,800 combined, a rise of 6.49 percent for the in-network figure (CMS 2027 file, Table 5). A plan can set a lower number, and most do: KFF’s 2026 average is $5,421 in-network ($4,636 for HMOs, $6,592 for PPOs) and $9,825 combined.

Where the Medigap premium comes in, and why we leave it blank

Medicare.gov is plain that “each insurance company decides how it will set the price” for Medigap, that for a given letter “the price is the only difference” between companies, and that premiums “typically increase each year.” There is no federal price table, so we publish none; the dataset lists the Plan G premium for your age, state and insurer as not verified, and a quote from a company, in writing, is the input you need.

With that input the comparison is a short piece of arithmetic. Let P(G) be the yearly Plan G premium and P(MA) the yearly Medicare Advantage plan premium, with the Part B premium identical on both sides and dropped out. Medigap costs P(G) plus up to $283 for the Part B deductible. Medicare Advantage costs P(MA) plus whatever cost sharing the year brings, from $0 up to the plan’s limit. Our arithmetic:

• In a year with almost no care, Medigap costs more than Medicare Advantage by P(G) less P(MA), plus the $283 deductible.
• In a year that reaches a $9,250 limit, Plan G costs less than Medicare Advantage only if P(G) less P(MA) is under $8,967 ($9,250 less $283).
• If the plan’s limit is the $5,421 average, that threshold is $5,138.
• Neither line includes Part D, the services a Medicare Advantage plan covers that Medigap does not, out-of-network charges, or the chance that your doctors and hospitals are in the plan’s network.

This is a framework, not a verdict on which product costs less for you. The answer moves with your health, your premiums and your network, which the page cannot see.

The one-way door: enrollment dates and guaranteed issue

The cost model above assumes you can buy what you choose. For Medigap that is not guaranteed, and the retiree’s timetable is the part most often wrong in the other direction (people assume they can try Medicare Advantage and return).

Source: Medicare.gov “When can I buy a Medigap policy?”, “Learn How Medigap Works”, “When does Medicare coverage start?” and “Joining a plan”. These are federal rights only; Medicare.gov says to “check with your State Insurance Department” for state rules, which we did not compile (not verified).

Read the table by the dates. The yearly election window closes on December 7, 2026 for coverage starting January 1, 2027. A retiree choosing Medicare Advantage for 2027 can generally leave in a later yearly window, but Medicare.gov ties the right to buy a Medigap policy without underwriting to the open enrollment period or to a listed situation, so the Medigap side may be harder to rebuild at 68 or 72 than it was at 65 (our reading of the Medicare.gov pages; Medigap policies, once bought, are “automatically renewed every year, even if you have health problems”).

Worked example (our arithmetic, hypothetical)

A joint couple with $250,000 of modified adjusted gross income in the lookback year is in tier 1: $284.10 a month each for Part B, $6,818.40 a year together, whichever coverage they choose. Take one spouse, a Plan G quote on one side and a Medicare Advantage plan with a $0 premium and a $6,750 in-network limit on the other. We make no assumption about the Plan G premium, so we write it as a variable.

Source: our arithmetic from the CMS tier 1 total ($284.10 times 12), the Part B deductible ($283) and an assumed $6,750 plan limit chosen only for illustration (the CMS intermediate ceiling for 2026). The result changes with every input, and the example ignores drugs, network and uncovered services.

For a reader at this income the Part B and IRMAA lines move together and cancel; what is left is the premium gap, the plan’s limit and the amount of care the household actually uses, which the household can estimate from its own claims history and an adviser or the State Health Insurance Assistance Program can check.

What to do with this

• Price the Part B line once. It is the same under both choices; a modified adjusted gross income change two years back (a sale, a conversion) moves it. See the Roth conversion calculator before a conversion, and the Form SSA-44 page if a life-changing event has cut your income.
• Get Plan G (or N) quotes in writing, from at least two insurers, for your state and age, and ask how each company has raised premiums over time. Medicare.gov says the benefits are identical across companies.
• Read the Medicare Advantage plan’s limit, not its star rating. Find the in-network and combined figures, the hospital and specialist copayments, and whether your own doctors and hospitals are in the network.
• Mark the dates (the federal rules are on Medicare.gov’s “When can I buy a Medigap policy?” page): December 7, 2026 for the yearly election window; the 60 days before and 63 days after a plan ends for any guaranteed-issue right; and the six-month Medigap open enrollment period if you are new to Part B.
• Do not count on getting Medigap later. If you choose Medicare Advantage now and want the option to move to Medigap, ask your State Insurance Department what your state allows (we did not verify state rules).
• Remember the exclusions. Medigap does not cover long-term care; see our hybrid long-term care insurance page for one way people fund it.

This page explains public rules and numbers from CMS, Medicare.gov and KFF. It is not insurance, tax or investment advice, and it does not recommend a product or a company. Each household’s answer depends on facts we cannot see; a licensed insurance agent or a State Health Insurance Assistance Program counselor can compare the actual plans and a CPA can say what your income does to your Part B premium. For a widow or widower dropping from joint to single brackets, the effect on IRMAA is on our widow’s tax penalty page.

Sources, read and saved on October 26, 2026: CMS fact sheet “2026 Medicare Parts A & B Premiums and Deductibles” (cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles); CMS “CY 2026 MOOP and Cost Sharing Limit Calculations” and “CY 2027 MOOP and Cost Sharing Limit Calculations” (cms.gov/medicare/payment/medicare-advantage-rates-statistics); Medicare.gov pages on costs, Medigap plan benefits, when to buy a Medigap policy, how Medigap works, Medigap costs, joining a plan, when coverage starts, penalties and coverage options; KFF “Medicare Advantage in 2026: Enrollment Update and Key Trends” (June 5, 2026) and “Medicare Advantage in 2026: Premiums, Out-of-Pocket Limits, Supplemental Benefits, and Prior Authorization”. We did not open ssa.gov for this page; the IRMAA tiers come from the CMS fact sheet and agree with our IRMAA page. All annual totals, gaps and thresholds are our arithmetic.

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