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. Notably, the first threshold rose from $106,000 in 2025 to $109,000 in 2026, a modest 2.83% increase tied to CPI inflation. That small adjustment means many retirees experienced bracket creep in 2026 without making any significant financial changes at all.

What the first bracket actually costs

The 2026 standard Part B premium is $202.90 a month. 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, plus another $174 in Part D surcharges at the same tier. Combined, 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. 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 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. But when one spouse dies, 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 at $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.

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 on their own. A Roth conversion, stock sale, RMD, or voluntary home sale does not qualify simply because it pushed MAGI over a threshold.

What to do

• 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 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, and the permanence of current tax rates under the One Big Beautiful Bill Act means that multi-year pacing remains a viable strategy without a rate-hike deadline looming.

• 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 is automatic.

• 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, can satisfy IRA distribution needs while keeping the donated amount entirely out of AGI, making it one of the most direct tools for IRMAA management available to retirees.

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 in the planning landscape is meaningful, 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 context on the 2.83% rise in the first IRMAA threshold from $106,000 in 2025 to $109,000 in 2026, the automatic Social Security deduction mechanic for enrollees already receiving benefits, and the effect of the One Big Beautiful Bill Act’s permanent tax rates on multi-year Roth conversion planning.

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