IRMAA: how one dollar of income can cost $974 a year
Most of Medicare’s cost sharing is proportional or flat. The income-related monthly adjustment is neither. It steps at a threshold, and it steps hard.
2026 first threshold, single filer
$109,001
At or below $109,000 of 2024 modified adjusted gross income the premium is $202.90. One dollar higher it is $284.10.
- Cost of that dollar
- $974over the year, Part B alone
- Top of the ladder
- $689.90per month
- Combined top charge
- $578.00Part B and Part D adjustments
- Income year used
- 2024two years back
Why it is a cliff and not a slope
Income tax works in marginal bands: crossing a threshold changes the rate on the next dollar only. IRMAA does not work that way. Crossing a threshold re-prices the entire premium for the whole year. There is no proportion, no taper and no partial tier.
The practical consequence is that a small, avoidable income event — a retirement account conversion, a capital gain, a one-off distribution — can cost far more in premium than it produced in income. Someone one dollar into the 2026 second bracket pays $974 more for Part B over the year than someone one dollar below it.
The two-year lag, which surprises people at exactly the worst moment
The premium is set by a return filed two years earlier. A person who retired last year is paying a premium priced on their final full year of employment income. The lag is at its most painful precisely when income has just fallen, which is the year most people start Medicare.
The fallback nobody documents
Where the return from two years back is not available to the agency, the one from three years back is used instead. That single sentence explains most cases where someone’s bracket appears to make no sense against the income they remember.
The 2026 brackets
| Single | Married filing jointly | Married filing separately | Adjustment | Total Part B | Part D adjustment |
|---|---|---|---|---|---|
| Up to $109,000 | Up to $218,000 | Up to $109,000 | none | $202.90 | none |
| $109,001 to $137,000 | $218,001 to $274,000 | — | $81.20 | $284.10 | $14.50 |
| $137,001 to $171,000 | $274,001 to $342,000 | — | $202.90 | $405.80 | $37.50 |
| $171,001 to $205,000 | $342,001 to $410,000 | — | $324.60 | $527.50 | $60.40 |
| $205,001 to $499,999 | $410,001 to $749,999 | $109,001 to $390,999 | $446.30 | $649.20 | $83.30 |
| $500,000 and above | $750,000 and above | $391,000 and above | $487.00 | $689.90 | $91.00 |
Married filing separately gets three tiers, not six
A married person who filed separately and lived with their spouse faces the standard premium up to the first threshold, then a jump straight to $649.20 a month, then the top tier. The intermediate brackets do not exist for that status. Tables that reuse the single-filer ladder for it are wrong.
What it does to an actual payment
| Standard | First income tier | |
|---|---|---|
| Gross monthly benefit | $3,084 | $3,084 |
| Part B premium | $202.90 | $284.10 |
| Net monthly payment | $2,881 | $2,799 |
| Over a year | $34,572 | $33,588 |
The difference is -$82 a month, -$984 a year — against a 2.8% adjustment worth +$84 a month on the same benefit. Crossing one bracket costs 1.0 times the entire raise.
And it disables hold harmless entirely
The provision that stops a Part B increase reducing a net payment does not apply to anyone in an income-related tier, at any income level. Paying IRMAA means paying every dollar of every future premium increase in full. The four exclusions.
Part D has its own ladder
The Part B adjustment is not the whole charge. A second, smaller adjustment applies to Part D, paid to Medicare directly rather than to the drug plan — including for people whose drug coverage sits inside a Medicare Advantage plan. At the top tier the two together come to $578.00 a month. The Part D ladder, and the formula that reproduces it exactly.
Bracket tables for 14 years are published on this site, each read from a primary source. The full set, and why some years are missing.
Common questions
What does IRMAA stand for?
Income-related monthly adjustment amount. It is an extra charge on Medicare Part B and Part D for beneficiaries above an income threshold, set by a tax return filed two years earlier.
Which year of income is used?
The 2024 return for 2026 premiums — two tax years back. Where that return is not available to the agency, the one from three years back is used instead. That fallback is undocumented in most summaries and is the usual explanation for a bracket that looks wrong.
Is there a phase-in across a bracket?
No. It is a cliff. One dollar over the 2026 first threshold moves the premium from $202.90 to $284.10 — an extra $974 over the year for that one dollar.
Can it be appealed?
A determination can be reconsidered where a life-changing event has reduced income since the tax year used — retirement, the death of a spouse, marriage or divorce, loss of a pension, and a small number of others. It is a defined list and a specific form, not a general hardship argument. This site does not advise on it; it states that the mechanism exists because most people do not know it does.
Related
- IRMAA by year14 tables
- 2026 bracketsin detail
- Part D IRMAAthe second charge
- Find your bracketcalculator
- Hold harmlessblocked by IRMAA
- The net raisethe study
Sources and freshness
- Federal Register — Medicare Program; Medicare Part B Monthly Actuarial Rates, Premium Rates, and Annual Deductible Beginning January 1, 2026 — verified 10 August 2026
- Federal Register — Medicare Program; Medicare Part B Monthly Actuarial Rates, Premium Rates, and Annual Deductible Beginning January 1, 2025 — verified 10 August 2026
- SSA POMS HI 01101.020 — Income-related monthly adjustment amount — verified 10 August 2026
Figures effective 1 January 2026. Page figures last verified against the sources above on 10 August 2026. Corrections: the correction log · support@inventum.com.au