Cross One IRMAA Line and Your Surcharge Doesn’t Nudge Up — It Jumps About $1,500 a Year

A single filer whose 2024 modified adjusted gross income came in at $137,500 just opened her first 2026 Medicare bill. Her neighbor, who landed at $136,500, pays the first-tier IRMAA surcharge. She pays the second tier. That $1,000 difference in income translates into roughly $1,700 more in annual Medicare premiums when Part B and Part D surcharges are combined. And she cannot undo it: the 2024 return is filed, and the 2026 premiums are already set.

If your household income runs well under the first IRMAA threshold, this article does not apply to you. IRMAA touches roughly 8% of people with Medicare Part B. The other 92% pay the standard premium and can stop reading. For the readers in that 8%, or anyone planning a Roth conversion, a home sale, or a large RMD, the bracket lines are the single most expensive math in Medicare.

An All-or-Nothing Bracket

IRMAA does not phase in. Cross a threshold by one dollar and you pay the full next-tier surcharge for the entire year. Here are the 2026 monthly Part B totals CMS published in November 2025, by single-filer MAGI from the 2024 tax return:

• $109,000 or less: $0 surcharge, $202.90 standard premium
• Over $109,000 to $137,000: $81.20 surcharge, $284.10 total
• Over $137,000 to $171,000: $202.90 surcharge, $405.80 total
• Over $171,000 to $205,000: $324.60 surcharge, $527.50 total
• Over $205,000 to under $500,000: $446.30 surcharge, $649.20 total
• $500,000 or more: $487.00 surcharge, $689.90 total

Joint filers see the same surcharges at $218,000, $274,000, $342,000, $410,000, and $750,000. Part D adds its own stack on top of whatever drug plan you carry: $14.50, $37.50, $60.40, $83.30, and $91.00 per month at the same income lines.

What the First Cliff Actually Costs

A single filer at $136,999 of MAGI pays the first-tier Part B surcharge of $81.20 a month. One dollar more and the surcharge jumps to $202.90. That is about $121.70 more a month, or roughly $1,460 more per year, on Part B alone. Part D steps up at the same line from $14.50 to $37.50 a month, adding about $276 more a year. The full cliff is roughly $1,500-plus per person per year, and IRMAA is deducted straight out of the Social Security check, where the 2.8% 2026 COLA is already spoken for.

For a married couple, every cliff counts twice. The jump from tier one to tier two costs the household roughly $3,000 a year. At the highest income levels, IRMAA becomes a substantial expense rather than a nuisance surcharge. The top tier, at $750,000 joint MAGI, can add well over $13,000 a year in Part B and Part D surcharges for a married couple compared with the standard premium structure.

The Traps Around the Cliff

Three mechanics catch readers off guard.

MAGI includes tax-exempt interest. For IRMAA, MAGI is line 11 of Form 1040 plus the tax-exempt interest on line 2a. Municipal bond income that feels tax-free still counts toward the bracket.

The two-year lookback locks the outcome. Your 2026 premium uses 2024 MAGI. A Roth conversion done in December 2024 set this year’s surcharge in stone before you saw your first Medicare bill.

The survivor trap. When one spouse dies, the survivor files single the next year. The single brackets sit at roughly half the joint brackets, so a household income that was comfortably under $218,000 can land above $137,000 single and trigger IRMAA for the first time. The bracket shifted while the income stayed flat.

SSA-44 reverses IRMAA only when income fell because of a qualifying life event: work stoppage, work reduction, marriage, divorce, death of a spouse, loss of pension, or loss of income-producing property. A Roth conversion, a stock sale, or a home sale will not qualify, no matter how badly it pushed you over a line.

What to Do

Three actions move the needle:

1. Model your projected MAGI for the current tax year against the bracket lines before December 31. If you are within $5,000 of a cliff, defer the next Roth conversion tranche, the next capital gain harvest, or the next discretionary IRA withdrawal into a year when you have room.
2. If you are 70½ or older, route charitable giving through a Qualified Charitable Distribution from your IRA. It satisfies RMDs without raising MAGI, and it is one of the few levers that lowers the IRMAA-relevant income line directly.
3. If your income dropped because of a qualifying life event, file Form SSA-44 with documentation (retirement letter, death certificate, divorce decree) and ask SSA to use your current expected income instead of the two-year-old return.

Figures reflect 2026 Medicare Part A, Part B, and Part D amounts released by CMS on November 14, 2025, applied to 2024 modified adjusted gross income.