Does a Roth Conversion Trigger IRMAA Surcharges?
"Fill your tax bracket." It is the most repeated Roth conversion advice in retirement planning, and it is how a lot of careful people accidentally buy themselves a Medicare surcharge. The advice is incomplete. It is missing a ceiling. Every dollar you convert from a traditional IRA to a Roth counts as ordinary income in the year you convert it, which means it feeds your modified adjusted gross income, which means Medicare looks at it two years later and prices your premiums accordingly. Fill the bracket, cross an IRMAA threshold by a dollar, and you have paid for a full tier of IRMAA surcharges to save a little tax.
The conversion that ate its own tax savings
Take a married couple, both 63, with $170,000 of base income from Social Security, pensions, and investment income. Their planner suggests converting $48,000 to Roth. Their joint MAGI lands at $218,000, exactly at the first 2026 IRMAA threshold, and they owe no surcharge at all. Clean.
Now suppose the same couple converts $150,000 instead, chasing the top of the 24 percent tax bracket, which stretches all the way to $403,550. Their MAGI hits $320,000. That lands in the $274,001 to $342,000 IRMAA tier, and the couple's combined Medicare surcharges run roughly $5,770 a year. The conversion was two years ago; the premiums are now. This is the part the bracket advice never mentions: the tax bracket you were filling extends far above the income line where Medicare starts charging you extra. The real ceiling was never the bracket. It was the IRMAA tier.
The marginal math gets worse at the edges. One analysis of a 63-year-old couple with $130,000 in other income found that the last $10,000 of a $150,000 conversion saved about $2,400 in federal tax at the 24 percent rate but triggered roughly $3,473 in IRMAA costs. That is a net loss of more than $1,000 on that last $10,000, an effective marginal rate near 59 percent. The conversion was still sensible in the aggregate. The last $10,000 of it was not.
Two ceilings, one conversion
Every Roth conversion in your 60s is constrained by two ceilings, and the lower one wins. The first is the top of your federal tax bracket. The second is the next IRMAA tier threshold minus your other projected income for the year. For 2026 premiums, the first joint threshold is $218,000 of MAGI and the second is $274,000, with corresponding single-filer lines at $109,000 and $137,000. Confirm the current year's figures on Medicare.gov before you execute, because the thresholds move annually. Our guide on lowering MAGI to avoid IRMAA covers the other levers that create headroom for a conversion.
The planning window matters as much as the sizing. Conversions completed before the IRMAA lookback window opens never touch your premiums. The income from the year you turn 63 sets your premiums for the year you turn 65 and enroll in Medicare, so the years between retirement and 63 are the golden window: convert aggressively then, and the surcharges never see the income. Later conversions can still be right. They are a trade with a price tag you should read before signing.
The expensive mistake is the accidental crossing: the conversion that lands $2,000 over a threshold nobody was watching, triggering a full tier of surcharges for a rounding error of tax savings. Size the conversion to the IRMAA line, not the tax bracket. Run your numbers through the IRMAA calculator before you execute.
The case for crossing on purpose
Here is where I will push back on the pure avoidance instinct. A single year of first-tier surcharges, about $1,148 per person per year at the lowest joint tier, can be a fine price for decades of tax-free growth and smaller required minimum distributions later. RMDs arrive every year from 73 onward and they are not optional; IRMAA from one conversion is one year. If the lifetime tax math favors the conversion by tens of thousands, do not let a one-year surcharge veto it. Just cross deliberately, with the number modeled, and never cross by a small accidental margin. That is the distinction that matters: priced-in surcharges are a cost, surprise surcharges are a mistake.
If you give to charity, there is a companion move worth knowing: qualified charitable distributions move IRA money to charity without touching MAGI at all, which can offset the income a conversion adds in the same year.
Frequently asked questions
Does a Roth conversion trigger IRMAA surcharges?
Yes. The full converted amount is ordinary income in the year of conversion and is included in MAGI, which sets your Medicare premiums two years later.
What is the safe conversion amount to avoid IRMAA?
Whatever keeps your projected MAGI, including the entire conversion, under the threshold for your filing status. For 2026 premiums the first thresholds are $109,000 single and $218,000 joint, based on 2024 MAGI. Thresholds change yearly, so confirm the current figures on Medicare.gov.
Can I undo a Roth conversion that triggered IRMAA?
Since 2018, the tax code no longer allows recharacterization, so you cannot undo a Roth conversion. Your remaining options are a Form SSA-44 appeal if you had a qualifying life-changing event, or simply absorbing one year of surcharges, since IRMAA resets annually.
Should I do my Roth conversions before age 63?
If you can, yes. Conversions completed before the IRMAA lookback window opens never affect your Medicare premiums. The tax year you turn 63 sets your first Medicare year's premiums, so the window between retirement and 63 is the most valuable conversion period.
Is it ever worth crossing an IRMAA tier on purpose?
Yes, when the lifetime tax savings clearly exceed one year of surcharges. A single year of first-tier surcharges is about $1,148 per person, which is small next to decades of tax-free compounding and reduced RMDs. Model both numbers and cross deliberately, never by accident.
Model Your Conversion Before You Execute
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