IRMAA is a cliff, not a slope. Crossing a threshold by one dollar moves you into the next bracket for the whole year, and the income it uses is not this year’s. Both facts are worth understanding before a year in which your income will be unusual.
The two-year lookback
IRMAA for a given year is set from the modified adjusted gross income on your tax return from two years earlier. So the 2026 surcharge is based on the return filed for 2024.
This is why it catches people who have just retired. The last two years of a working life are often the highest-earning, and the surcharge arrives in the first year of a much smaller income. It is also why a one-off event — selling a property, converting a retirement account, taking a lump sum — shows up as a higher Medicare premium two years later, when the money is long spent.
The 2026 brackets
| Individual return | Joint return | Part B total monthly premium | Part D monthly add-on |
|---|---|---|---|
| $109,000 or less | $218,000 or less | $202.90 | $0.00 |
| Over $109,000 to $137,000 | Over $218,000 to $274,000 | $284.10 | $14.50 |
| Over $137,000 to $171,000 | Over $274,000 to $342,000 | $405.80 | $37.50 |
| Over $171,000 to $205,000 | Over $342,000 to $410,000 | $527.50 | $60.40 |
| Over $205,000 and under $500,000 | Over $410,000 and under $750,000 | $649.20 | $83.30 |
| $500,000 or more | $750,000 or more | $689.90 | $91.00 |
Source: CMS, 2026 Medicare Parts A & B Premiums and Deductibles, published November 14, 2025. The Part D figure is an amount added to whatever your plan charges, not a total.
People who are married, lived with their spouse during the year and file separately have their own three-row schedule: $0 at $109,000 or less, $446.30 added to Part B and $83.30 to Part D above $109,000 and under $391,000, and $487.00 and $91.00 at $391,000 or more.
The two surcharges behave differently
The Part B column is a total premium: it already includes the standard $202.90. The Part D column is an addition to whatever your plan charges, so a plan with a $30 premium becomes $67.50 in the third bracket rather than $37.50.
The Part D surcharge is deducted from a Social Security payment or billed by Medicare directly, not collected by the plan, which is why it can appear as a separate and unexpected charge.
When the lookback is simply wrong about you
If your income has fallen because of a life-changing event, the two-year-old return no longer describes you, and you can ask Social Security to use a more recent year instead. The recognised events include marriage, divorce, the death of a spouse, work stoppage or reduction, loss of income-producing property, and loss of a pension.
This is a form-based process run by Social Security rather than by Medicare, and it is worth doing promptly: retiring is one of the listed events, and retirement is the single most common reason a bracket is wrong.
Note what is not on the list. A one-off capital gain is not a life-changing event. Selling a house the year before you retire will raise your premium two years later and there is no appeal on those grounds — which is an argument for knowing the thresholds before the sale, not after.
Frequently asked questions
What income year does my 2026 IRMAA use?
Your 2024 tax return. IRMAA uses the modified adjusted gross income from the return filed two years before the premium year.
Is IRMAA a percentage of my income?
No. It is a bracket system with fixed amounts, and the brackets are cliffs. One dollar over a threshold puts you in the next bracket for the whole year.
I just retired and my income has dropped. Can I do anything?
Yes. Work stoppage or reduction is a recognised life-changing event, so you can ask Social Security to use a more recent year instead of the two-year-old return. Do it promptly rather than waiting for the premium to correct itself, because it will not.
Does the Part D figure replace my plan premium?
No. The Part D amount is added to whatever your plan charges. The Part B figure in the table, by contrast, is the total monthly premium including the standard amount.
Sources
- 2026 Medicare Parts A & B Premiums and Deductibles — Centers for Medicare & Medicaid Services · 2025-11-14 · read 2026-10-19
- Medicare costs — Medicare.gov · read 2026-10-19
This guide explains published rules and figures, with the source for each one. It is not advice about your own situation.