A 67-year-old couple opened their January 2026 Social Security deposit and found nearly $500 less than they expected. The culprit was a Roth conversion they ran in 2024 to lock in lower brackets before they thought rates might rise. The conversion did exactly what they planned for taxes. It also pushed their modified adjusted gross income from two years prior into a Medicare income-related surcharge bracket they had never heard of.
This article is for the small slice of Medicare beneficiaries who will trip this wire. CMS says income-related Part B adjustments affect about 8% of people with Medicare Part B. If your household MAGI was comfortably under the first threshold in 2024, IRMAA may not affect your 2026 Medicare bill. If 2024 was the year you sold a rental, took a large required minimum distribution, ran a Roth conversion, or collected a severance payment, keep reading.
The Two-Year Lookback, in Plain Dollars
Medicare generally bases your 2026 Part B and Part D surcharges on the MAGI reported on your 2024 federal tax return, and Social Security makes the IRMAA determination using IRS data. The determination letter identifies the tax year used, the income amount, and the surcharge. MAGI for IRMAA is your adjusted gross income from Form 1040, line 11, plus tax-exempt interest from line 2a. Municipal bond income that feels tax-free still counts here.
The 2026 standard Part B premium is $202.90. Above the first bracket, the surcharges stack on top of that base, per person, every month:
| 2024 MAGI (single) | 2024 MAGI (joint) | Part B total premium (per person, monthly) | Part D surcharge (per person, monthly) |
|---|---|---|---|
| ≤ $109,000 | ≤ $218,000 | $202.90 | $0.00 |
| $109,001 to $137,000 | $218,001 to $274,000 | $284.10 | $14.50 |
| $137,001 to $171,000 | $274,001 to $342,000 | $405.80 | $37.50 |
| $171,001 to $205,000 | $342,001 to $410,000 | $527.50 | $60.40 |
| $205,001 to under $500,000 | $410,001 to under $750,000 | $649.20 | $83.30 |
| ≥ $500,000 | ≥ $750,000 | $689.90 | $91.00 |
The couple in the open had $215,000 of MAGI in 2024 before the conversion, which would have landed them in the standard bracket. A $60,000 Roth conversion pushed them to $275,000. That puts them in the third joint tier, costing $405.80 more per month combined in Part B surcharges plus $75 in Part D surcharges. Their 2.8% Social Security COLA did not come close to covering it.
IRMAA is cliff-edged. One extra dollar of MAGI over a threshold moves you into the entire next tier for the whole year. A couple at $274,001 pays the third-tier premium; at $274,000 they pay the second.
What SSA-44 Will and Will Not Fix
Readers routinely assume they can appeal an IRMAA surcharge tied to any one-time event. They can request a reduction only for a narrow list of qualifying life-changing events: marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, loss of income-producing property, loss of pension income, or certain employer settlement payments. Form SSA-44 can reduce IRMAA when household income fell because of one of these events.
A Roth conversion does not qualify. Neither does a voluntary home sale, a large RMD, or a capital gains harvest. If the income event was elective, the surcharge stands.
The second trap is the survivor scenario. A surviving spouse may still be able to file jointly for the year of death, and some surviving spouses with dependent children may qualify for favorable filing status for two more years. Many older survivors eventually file as single, where the IRMAA brackets are roughly half the joint ones. The same income can newly trigger IRMAA or jump a tier. Death of a spouse is a qualifying SSA-44 event when it reduces household income.
What to Do Before December 31
Plan income two calendar years ahead of the Medicare year you care about. Your 2026 income generally drives your 2028 premium. If you are weighing a Roth conversion, a property sale, or accelerated IRA withdrawals in 2026, model the MAGI total against the applicable thresholds above and stop short of the next cliff unless the tax savings clearly justify the surcharge.
Open the SSA determination letter as soon as it arrives. It states the tax year used, the MAGI figure, and the surcharge amount. If the income shown is wrong, follow the appeal instructions in the notice. If a qualifying life-changing event has reduced your income since 2024, file Form SSA-44 promptly with documentation, such as a death certificate, proof of work stoppage, or an employer settlement notice.
If your projected 2026 MAGI sits within $20,000 of any IRMAA threshold, the surcharge math may justify a one-time session with a fee-only advisor who builds tax-efficient withdrawal sequences. A single bracket mistake can cost hundreds of dollars a month for a couple, so the planning fee may be easier to justify than it first appears.
The Conversion May Still Be Right
A Roth conversion is not automatically a mistake just because it triggers IRMAA. The problem is finding out two years later, after the tax year is closed and the Medicare surcharge is locked in. Before converting, selling, or accelerating withdrawals, retirees should price the tax savings and the Medicare cliff together.
Source note: 2026 premium and IRMAA figures are from the CMS fact sheet “2026 Medicare Parts A & B Premiums and Deductibles,” released November 14, 2025. COLA figure and SSA-44 life-changing event rules are from the Social Security Administration.
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