A man turns 65, enrolls in Medicare, and opens his first premium notice expecting the standard rate. Instead, the number is roughly double. He did nothing wrong that year. The damage was done two years earlier, at age 63, when his advisor walked him through a Roth conversion designed to fill the 24% bracket before required minimum distributions became an issue. The conversion was mathematically sound. But the retiree and advisor didn’t consider the Medicare consequences.
Medicare’s Income-Related Monthly Adjustment Amount, known as IRMAA, uses modified adjusted gross income from two years prior to set the current year’s Part B and Part D surcharges. Enroll at 65, and Social Security pulls your tax return from age 63. That’s the age at which many pre-retirees do aggressive Roth conversions, because they are no longer working, have not yet claimed Social Security, and want to move money out of traditional IRAs before RMDs begin.
A $180,000 conversion stacked on top of even modest interest, dividends, or part-time income easily pushes a single filer past the second IRMAA cliff. The surcharges jump at each threshold, and one dollar over triggers the entire next tier.
For 2026, the standard Part B premium is $202.90 per month. The tiers for a single filer:
- MAGI at or below $109,000: standard premium of $202.90, no surcharge.
- MAGI between $109,000 and $137,000: total premium of $284.10.
- MAGI between $137,000 and $171,000: total premium of $405.80.
- MAGI between $171,000 and $205,000: total premium of $527.50.
- MAGI between $205,000 and $500,000: total premium of $649.20.
A $180,000 conversion added to a few thousand in taxable interest lands in the third tier. The full-year surcharge on Part B, plus the parallel Part D surcharge, comes to a few thousand dollars for a single filer.
The Social Security Administration allows appeals via Form SSA-44 for life-changing events: retirement, marriage, divorce, death of a spouse, loss of pension, or work reduction. A Roth conversion is not on that list. Voluntary income does not qualify.
The Fix He Wishes He Had Known
Two strategies would have prevented this outcome.
The stronger path is to finish large conversions by the year you turn 62. Any conversion income in that year and earlier never touches IRMAA, because the lookback window sits before Medicare eligibility. For someone with a $1.2 million portfolio and a multi-year conversion plan, this alone can move six figures of taxable IRA money into a Roth without surcharge exposure.
The secondary path is to size each conversion to stop just under an IRMAA threshold from age 63 onward. Treat the $109,000 and $137,000 single-filer lines as hard ceilings that override bracket-based conversion sizing. The federal 24% bracket for a single filer in 2026 runs up to $201,775, which is why bracket-focused advice routinely blows past IRMAA cliffs. The Medicare cliff sits well below the top of the 24% bracket.
Converting anyway can still be correct. If avoiding a future RMD at a 32% or 35% rate is on the table, a one-year surcharge measured in the low four figures may be worth accepting. The point is to know the cost before signing the paperwork.
What to Do This Year
Anyone between 60 and 64 with a seven-figure traditional IRA should pull two numbers before scheduling another conversion: projected MAGI for the current year, and the IRMAA threshold immediately above it. If the conversion crosses a threshold, price the surcharge explicitly and decide whether the long-term Roth benefit justifies it.
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