Quick Answer
Medicare's income-related monthly adjustment amount, or IRMAA, is set from the tax return you filed two years earlier. Your 2026 Part B and Part D premiums come from your 2024 modified adjusted gross income. Income you generate in 2026 — including a Roth conversion — determines your 2028 premium and does nothing at all to 2026 or 2027.
The second thing to know is that IRMAA is a cliff. There is no phase-in. Under the 2026 schedule a single filer at $109,000 of MAGI pays no surcharge; at $109,001 the surcharge is $95.70 per month, or $1,148.40 for the year, per person. One dollar of income costs more than a thousand dollars of premium.
Put together, these two facts change how a conversion should be sized. If your other 2026 income is $95,000 as a single filer, our engine says you can convert $14,000 and land exactly on the $109,000 line with no surcharge. Convert $40,000 instead and you have bought yourself a $1,148.40 Medicare bill — payable in 2028.
Key Takeaways
- Two-year lag, both directions. A high-income year shows up on your premium two years later; so does a low-income year, which is why the surcharge disappears on its own
- One year of income, one year of surcharge. IRMAA is redetermined annually, so a single conversion does not create a permanent increase
- It is a cliff at every tier, not just the first — and the jumps get larger as you go up
- It is charged per person. A couple where both spouses are on Medicare pays the surcharge twice
- Tax-exempt interest counts. MAGI for IRMAA is AGI plus municipal bond interest, which surprises people who hold munis specifically to keep income down
- A voluntary conversion is not an appealable event. Form SSA-44 covers income that fell for one of eight listed reasons; choosing to convert is not one of them
What a General AI Assistant Says, and What Is Actually True
This is a documented, dated, checkable answer — not a claim that assistants always get IRMAA wrong. Many explain the two-year lookback correctly when you ask about it directly. The failure we want to name is narrower and more common: the lookback gets dropped when the question is about something else, such as a Roth conversion. The model answers the conversion question and quietly applies this year's income to this year's brackets.
Answering from training data, with no tools connected
Tested: August 8, 2026. Prompt: “I am 66 and on Medicare. My income in 2026 will be about $95,000. If I do a $40,000 Roth conversion this year, will my Medicare premiums go up?”
A commonly reproduced answer: “Yes. The conversion would put your MAGI at $135,000, which is above the $106,000 IRMAA threshold for single filers, so your Medicare Part B and Part D premiums for 2026 would increase.”
Two errors, one of them expensive:
- Wrong year. A 2026 conversion cannot change a 2026 premium. Premiums for 2026 were set from the 2024 return. This conversion lands on 2028. Someone who acts on the answer as given may cancel a conversion to avoid a cost that was never going to arrive when they were told, or — worse — may skip the actual planning conversation about 2028
- Stale threshold. $106,000 was the 2025 first-tier figure. The 2026 threshold is $109,000. The conclusion happens to survive the error here because $135,000 clears both, but a filer sitting between $106,000 and $109,000 would be told they owe a surcharge they do not
Why this particular failure recurs. The lookback is a temporal rule, and temporal rules are the hardest thing for a system with no clock to apply. A model has no reliable sense of what “this year” is at the moment you ask, so the safest-seeming move is to treat the income year and the premium year as the same year. That is right for almost every other tax question and wrong for this one. Layer on annually re-indexed thresholds and you have a rule that requires both a current date and a current table — two things weights cannot hold.
Assistants are useful here. They explain what IRMAA is well. They should not be the source of the number or the year.
The Same Question Through a Deterministic Engine
Our Roth conversion calculator runs the same IRMAA engine used below. Given a base MAGI of $95,000, a $40,000 conversion and single filing status, it returns the following against the 2026 schedule.
| Field | Value |
|---|---|
| Tier before conversion | Tier 0 — no surcharge |
| Tier after conversion | Tier 1 |
| Part B surcharge | $81.20 per month |
| Part D surcharge | $14.50 per month |
| Monthly increase | $95.70 |
| Annual increase, per person | $1,148.40 |
| Largest conversion with no tier change | $14,000 |
| Distance to the next threshold | $14,001 |
An honest caveat about the 2028 number
The figures above are computed against the 2026 schedule, because that is the most recent one CMS has published. A conversion done in 2026 is actually assessed against the 2028 thresholds and surcharges, which will not exist until CMS publishes them in late 2027. Thresholds are indexed and generally drift upward, so the 2026 table is a reasonable planning proxy and not a quotation. Treat the $14,000 headroom figure as “approximately, under today's rules,” and leave yourself a margin.
We would rather tell you the number has a known limit than present it as precise. That distinction is the point of the whole page.
2026 IRMAA Brackets and Surcharges
These are the surcharges you pay in 2026, determined by the MAGI on your 2024 return. The standard Part B premium for 2026 is $202.90 per month; the surcharge is added on top of it. All amounts are per person.
| 2024 MAGI | Part B surcharge | Part D surcharge | Total per month | Total per year |
|---|---|---|---|---|
| $109,000 or less | $0.00 | $0.00 | $0.00 | $0.00 |
| $109,001 to $137,000 | $81.20 | $14.50 | $95.70 | $1,148.40 |
| $137,001 to $171,000 | $202.90 | $37.50 | $240.40 | $2,884.80 |
| $171,001 to $205,000 | $324.60 | $60.40 | $385.00 | $4,620.00 |
| $205,001 to $499,999 | $446.30 | $83.30 | $529.60 | $6,355.20 |
| $500,000 and above | $487.00 | $91.00 | $578.00 | $6,936.00 |
| 2024 MAGI | Part B surcharge | Part D surcharge | Total per month | Per year, per spouse |
|---|---|---|---|---|
| $218,000 or less | $0.00 | $0.00 | $0.00 | $0.00 |
| $218,001 to $274,000 | $81.20 | $14.50 | $95.70 | $1,148.40 |
| $274,001 to $342,000 | $202.90 | $37.50 | $240.40 | $2,884.80 |
| $342,001 to $410,000 | $324.60 | $60.40 | $385.00 | $4,620.00 |
| $410,001 to $749,999 | $446.30 | $83.30 | $529.60 | $6,355.20 |
| $750,000 and above | $487.00 | $91.00 | $578.00 | $6,936.00 |
Every surcharge above is engine output, sourced to the CMS 2026 premium schedule published November 14, 2025. Married-filing-separately uses a different and much more compressed schedule; see the CMS release if that is your status. Annual figures are per enrolled person — a couple where both spouses are on Medicare and whose 2024 MAGI was $240,000 pays $1,148.40 each, or $2,296.80 for the household.
The surcharge amounts are not arbitrary. Part B is designed so that most beneficiaries pay about 25% of program cost; IRMAA raises that share to 35%, 50%, 65%, 80% and 85% across the five tiers. That is why the tier-2 Part B surcharge of $202.90 is exactly the standard premium — at 50% you are paying double the ordinary 25% share.
It Is a Cliff, and the Cliff Gets Steeper
Income tax works in marginal brackets: earning one dollar into a higher bracket taxes only that dollar at the higher rate. IRMAA does not work that way. Crossing a threshold by any amount moves your entire premium to the next tier for the whole year.
| Crossing this 2024 MAGI line | Annual cost of that $1 |
|---|---|
| $109,000 to $109,001 | $1,148.40 |
| $137,000 to $137,001 | $1,736.40 |
| $171,000 to $171,001 | $1,735.20 |
| $205,000 to $205,001 | $1,735.20 |
| $499,999 to $500,000 | $580.80 |
Each row is the difference between two engine tier lookups one dollar apart. Figures are per person, per year.
A worked example from the engine: a single filer with $108,500 of MAGI who converts $1,000 moves to $109,500 — $500 over the line. The conversion produces roughly $220 of federal income tax at a 22% marginal rate, and $1,148.40 of Medicare surcharge. The effective cost of that last $500 of conversion is well over 100%.
Tax-exempt interest is the usual culprit
MAGI for IRMAA is Form 1040 line 11 (adjusted gross income) plus line 2a (tax-exempt interest). Municipal bond income that pays no federal income tax still counts toward these thresholds. Households that hold munis specifically to manage taxable income are the ones most likely to size a conversion against AGI, ignore the muni interest, and cross a line they thought they were $5,000 clear of. Check line 2a before you compute your headroom.
What the Two-Year Lag Means for Conversion Timing
The lag is not only a hazard. It is also a window, and it closes at a specific age.
Conversions before age 63 do not touch Medicare at all
If you turn 65 in a given year, the premium for that year comes from the return you filed for the year you turned 63. Conversions completed at 62 and earlier land on premium years before you are enrolled, so they carry no IRMAA consequence whatsoever. For anyone planning a multi-year conversion ladder, the years from retirement to age 62 are the ones with the fewest constraints — earned income has stopped, Social Security may not have started, and Medicare is not yet listening.
Age 63 is when the meter starts
A conversion in the year you turn 63 sets your premium for the year you turn 65 — your first Medicare year. This is the single most commonly missed transition, because nothing about turning 63 feels Medicare-related.
Size against the line, not against the tax bracket
Because IRMAA is a cliff and income tax is a slope, the binding constraint on a conversion is frequently the IRMAA threshold rather than the top of a tax bracket. The engine reports both distances:
- Single filer, $95,000 of other income: $14,000 of conversion room before the first threshold
- Married filing jointly, $200,000 of other income: $18,000 of conversion room before the first threshold
Splitting a large conversion across two or three calendar years to stay under a line in each of them is a standard response, and one our conversion strategy guide works through in more detail.
The surcharge is temporary by design
IRMAA is redetermined every year from a fresh return. A single high-income year produces a single year of surcharge, after which your premium returns to the standard amount without you doing anything. That matters for the arithmetic: a $1,148.40 one-year cost against a conversion that removes decades of future required minimum distributions may be perfectly rational. It is a cost to price, not automatically a reason to stop.
When you can appeal, and when you cannot
Form SSA-44 lets you ask Social Security to use a more recent year's income when a life-changing event has reduced it. The eight qualifying events are marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property, loss of pension income, and an employer settlement payment or closure. Retiring is the most commonly used one — a new retiree assessed on their final working year has a strong case.
A Roth conversion is not a qualifying event. It is a voluntary increase, not an involuntary decrease, so there is no appeal path for a surcharge you triggered yourself. Plan for it up front, because there is no remedy afterward.
Check This Yourself in Two Minutes
- Ask your assistant, with no tools or web browsing enabled: “I am 66 and on Medicare. My income in 2026 will be about $95,000. If I do a $40,000 Roth conversion this year, will my Medicare premiums go up?”
- Check which year it names. Any answer that says your 2026 premium will rise has dropped the two-year lookback. The correct premium year is 2028
- Check the threshold it used. $106,000 is the 2025 figure and $103,000 is 2024. The 2026 first-tier threshold is $109,000
- Check whether it said “per person.” For a married couple both on Medicare the surcharge applies twice, and an answer that quotes a single figure for a household is understating by half
- Verify against the primary source: the CMS 2026 Medicare Parts A & B premiums fact sheet(opens in new tab) states the thresholds and surcharges directly
If your assistant handles all four points correctly, that is a good result and worth knowing. If you believe a figure on this page is wrong, tell us through the about page — we correct dated content and note when we did.
Find your own headroom before you convert
The calculator takes your MAGI, filing status and age, applies the current IRMAA schedule, and reports how much you can convert before the next threshold and what crossing it would cost.
Sources
- CMS — 2026 Medicare Parts A & B premiums and deductibles (published November 14, 2025)(opens in new tab)
- Social Security Administration — Request to lower an Income-Related Monthly Adjustment Amount(opens in new tab)
- Form SSA-44 — Medicare IRMAA Life-Changing Event(opens in new tab)
- 42 U.S. Code Section 1395r — Amount of Part B premium, including the income-related adjustment(opens in new tab)
- 20 CFR Part 418 — Medicare subsidies and income-related monthly adjustment amounts(opens in new tab)
Important Disclaimer
Disclaimer: This content is for educational and informational purposes only and does not constitute financial, tax, or legal advice. IRMAA thresholds and surcharges are re-set annually by CMS; the figures here are the published 2026 schedule and are used as a planning proxy for later years, which have not been published. A Roth conversion has income tax, state tax, Social Security taxation and estate consequences beyond the Medicare surcharge discussed here. Individual circumstances vary, and you should consult a qualified tax or financial professional before converting. While we strive for accuracy, laws and regulations change frequently. Data current as of August 2026.
Content reviewed by Mark at Markco Labs. Learn more about our accuracy standards.
Frequently Asked Questions
Your 2024 tax return. Medicare's income-related monthly adjustment amount uses modified adjusted gross income from two years prior, because that is the most recent return the IRS has finished processing when Social Security sets premiums each autumn. Income you earn in 2026 determines your 2028 premium.
Yes, but not this year. A conversion completed in 2026 increases 2026 MAGI, which Social Security uses to set 2028 premiums. Nothing about your 2026 or 2027 premium changes. The surcharge also applies for one year only, because IRMAA is redetermined annually from a fresh tax return, so a single large conversion produces a single year of higher premiums rather than a permanent increase.
It is a cliff. There is no phase-in and no marginal calculation. Under the 2026 schedule a single filer with MAGI of $109,000 pays no surcharge, and a single filer at $109,001 pays $95.70 per month more for Part B and Part D combined, or $1,148.40 for the year. One dollar of additional income can cost over a thousand dollars, which is why a conversion sized to land just under a threshold behaves very differently from one sized just over it.
Adjusted gross income from Form 1040 line 11 plus tax-exempt interest from line 2a. The inclusion of tax-exempt interest is the detail most often missed: municipal bond income that is free of federal income tax still counts toward the IRMAA threshold. Roth conversions, capital gains, IRA distributions and the taxable portion of Social Security all flow through AGI and therefore all count.
Per person. A married couple filing jointly is measured against the joint thresholds, but if both spouses are enrolled in Medicare they each pay the surcharge. At the 2026 first tier that is $1,148.40 each, or $2,296.80 for the household, for one year of elevated income.
Generally no. Form SSA-44 lets you request a reduction when a qualifying life-changing event has reduced your income, and the eight qualifying events are marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property, loss of pension income, and an employer settlement payment. A voluntary Roth conversion is not among them. The appeal path exists for income that fell, not for a one-time increase you chose.