A 66-year-old retiree in a personal finance forum recently posted that her 2024 Roth conversion, meant to shrink future required minimum distributions, pushed her single-filer income to $112,000. Two years later, her 2026 Medicare bill arrived with a surcharge attached. She had crossed the first IRMAA bracket by $3,000 and now owes an extra sum every month for the rest of the year, on both Part B and Part D.
IRMAA hits roughly 8% of Part B enrollees. The risk is concentrated among retirees whose modified adjusted gross income is near the 2026 thresholds of $109,000 for single filers or $218,000 for joint filers. A Roth conversion, home sale, capital gain, or RMD can push income over the first cliff two years before the Medicare bill arrives.
What the first bracket actually costs
The 2026 standard Part B premium is $202.90 a month. Cross the first IRMAA threshold, MAGI above $109,000 for single filers or $218,000 for joint filers, and Medicare adds a Part B surcharge of $81.20 a month, lifting the total to $284.10. Annualized, that is $974.40 in extra Part B premium per person, plus another $174 for the Part D surcharge at the same tier.
Combine Part B and Part D and the first-bracket enrollee pays $1,148.40 per year in surcharges on top of standard premiums. A married couple where both spouses cross the joint threshold pays $2,296.80. At the top tier, MAGI of at least $500,000 for single filers or $750,000 for joint filers, the Part B surcharge alone climbs to $487.00 a month per person.
The MAGI trap
IRMAA uses MAGI, which for Medicare purposes is your Form 1040 line 11 adjusted gross income plus tax-exempt interest from line 2a. Municipal bond interest that feels tax-free still counts here. So does the taxable portion of a Roth conversion, taxable capital gains from a home sale above the $250,000/$500,000 exclusion, and RMDs. Social Security benefits count only to the extent they are taxable, but a conversion can make more of those benefits taxable.
The lookback is the piece many enrollees miss. Your 2026 premium generally reflects the MAGI on your 2024 tax return. A conversion done in 2024 can hit the mailbox in January 2026. A conversion done in 2026 generally sets your 2028 premium. That two-year lag means the window to manage the trigger often closes before the bill arrives.
The survivor trap
The joint threshold is roughly double the single threshold. When one spouse dies, the survivor may eventually file as single, and the same income then measures against a bracket half as wide. A couple at $200,000 joint MAGI is under the $218,000 line, but a survivor at $150,000 single MAGI would fall into the second IRMAA tier under the 2026 brackets. The portfolio may not have changed, but the filing status did.
What SSA-44 will and will not do
Form SSA-44 requests an IRMAA recalculation when a qualifying life-changing event drops your income: marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, certain losses of income-producing property, loss of pension income, or an employer settlement payment. It does not cover voluntary income events by themselves. A Roth conversion, stock sale, RMD, or voluntary home sale will not qualify just because it pushed MAGI higher.
What to do
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Model MAGI before executing a conversion or lumpy withdrawal. If a $50,000 Roth conversion would push you from $105,000 to $155,000 MAGI, you would move past the first IRMAA tier and into the second tier under the 2026 single-filer brackets. Splitting the conversion across two tax years may keep each year below a higher threshold.
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If a qualifying life-changing event dropped your income, request a new determination with SSA-44 and attach documentation such as a retirement letter, death certificate, or employer notice. Do not assume the correction is automatic. It is not.
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If a surviving spouse’s projected single-filer MAGI lands within $20,000 of a bracket, get tax modeling done before December. A qualified charitable distribution, available beginning at age 70½ and capped at $111,000 for 2026, can satisfy IRA distribution needs while keeping the donated amount out of AGI.
Plan the Conversion Before Medicare Prices It
A Roth conversion can still be smart retirement planning. The mistake is treating it as only an income-tax decision. Once MAGI crosses an IRMAA line, the Medicare surcharge arrives two years later and applies for the full premium year. The cleanest fix is not an appeal after the bill arrives. It is modeling the conversion before December 31.
Sources: 2026 Medicare premium, IRMAA threshold, and surcharge figures come from CMS’s “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet. SSA-44 qualifying events come from Social Security Administration Form SSA-44 and SSA’s IRMAA guidance. Roth conversion tax treatment comes from IRS IRA guidance. The 2026 QCD limit comes from IRS Notice 2025-67.
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