IRMAA Has Five Income Brackets. Crossing Just the First Costs You About $900 a Year.

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 amount every month for the rest of the year, on both Part B and Part D.

IRMAA affects roughly 8% of Part B enrollees. The risk is concentrated among retirees whose modified adjusted gross income lands near the 2026 thresholds: $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. The first threshold rose from $106,000 in 2025 to $109,000 in 2026, a modest 2.83% increase tied to CPI inflation, while the surcharge amounts themselves jumped roughly 9%. That combination means some retirees stayed below the bracket line but still paid more once they crossed it.

What the first bracket actually costs

The 2026 standard Part B premium is $202.90 a month, up $17.90 from $185.00 in 2025. Cross the first IRMAA threshold 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. Add the Part D surcharge at the same tier, $14.50 a month, and the first-bracket enrollee pays $1,148.40 per year above standard premiums. A married couple where both spouses cross the joint threshold pays $2,296.80 in added costs annually.

At the top tier, where MAGI reaches 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, bringing the total monthly Part B bill to $689.90. The surcharge is collected automatically for those receiving Social Security benefits, deducted directly from their monthly payment. Retirees who have not yet claimed Social Security receive a separate quarterly bill from CMS instead, which can catch people off guard in the first year.

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 large conversion can make more of those benefits taxable, creating a compounding effect on MAGI.

The lookback is the piece many enrollees miss. Your 2026 premium 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 sets your 2028 premium. That two-year lag means the window to manage the trigger often closes before the bill arrives, and by then there is no appeal available for a voluntary income decision.

The survivor trap

The joint threshold is roughly double the single threshold, which makes the math look manageable for couples. When one spouse dies, however, the survivor files as single, and the same income suddenly measures against a bracket half as wide. A couple at $200,000 joint MAGI is comfortably below the $218,000 line. A survivor carrying $150,000 in single-filer MAGI falls into the second IRMAA tier under 2026 brackets. The portfolio may not have changed at all. The filing status did, and that alone is enough to trigger a surcharge that can persist for years.

What SSA-44 will and will not do

Form SSA-44 requests an IRMAA recalculation when a qualifying life-changing event has reduced your income. The qualifying events are: marriage, divorce or annulment, death of a spouse, work stoppage, work reduction, certain losses of income-producing property, loss of pension income, and an employer settlement payment. The form does not cover voluntary income events. A Roth conversion, stock sale, RMD, or voluntary home sale does not qualify simply because it pushed MAGI over a threshold, and filing the form in those circumstances will not result in a reduction.

What to do

• Model MAGI before executing a conversion or a large one-time withdrawal. If a $50,000 Roth conversion would push you from $105,000 to $155,000 in MAGI, you would clear the first IRMAA tier and land in the second under the 2026 single-filer brackets. Splitting the conversion across two tax years may keep each year below a higher threshold. The One Big Beautiful Bill Act made current federal tax rates permanent, removing any urgency to convert ahead of a rate-hike deadline, so multi-year pacing is a viable strategy without the old sunset pressure.

• If a qualifying life-changing event dropped your income, request a new determination using SSA-44 and attach supporting documentation such as a retirement letter, death certificate, or employer notice. Do not assume the correction happens automatically.

• If a surviving spouse’s projected single-filer MAGI lands within $20,000 of a bracket, complete tax modeling before December. A qualified charitable distribution, available beginning at age 70½ and capped at $111,000 per person for 2026, satisfies IRA distribution requirements while keeping the donated amount entirely out of AGI. That makes it one of the most direct IRMAA-management tools available to retirees, and its value grew further under the One Big Beautiful Bill Act, which introduced new limits on itemized charitable deductions that make the QCD’s income-exclusion structure more attractive by comparison.

Plan the conversion before Medicare prices it

A Roth conversion can still be sound retirement planning. The mistake is treating it as purely 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 One Big Beautiful Bill Act made current federal tax rates permanent, removing the urgency of converting before rates rose. That shift is meaningful for multi-year planning, but it does not eliminate the IRMAA risk. The two-year lookback still runs, the MAGI cliffs are unchanged, and the surcharges are real. The most effective fix is not an appeal after the bill arrives. It is modeling the conversion against MAGI thresholds 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. OBBBA tax rate changes are drawn from the One Big Beautiful Bill Act, signed July 4, 2025.

Editor’s note: This update adds the Part B 2026 premium increase from $185.00 to $202.90 (a $17.90 jump), notes that IRMAA surcharge amounts themselves rose roughly 9% in 2026 even as thresholds rose only about 3%, and expands the QCD section to reflect how the One Big Beautiful Bill Act’s new limits on itemized charitable deductions make the QCD income-exclusion route more advantageous for retirees managing MAGI.

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