One day an envelope from Social Security shows up and your Medicare premium has quietly gone up — sometimes a lot. It has a name almost nobody hears until it hits them: IRMAA, the income-related monthly adjustment amount. It's a surcharge added on top of your standard Part B and Part D premiums when your income is above certain lines. Here's the honest version: what triggers it, why it's based on income from two years ago, why it behaves like a cliff, and how to push back.
What IRMAA actually is
Most people on Medicare pay the standard Part B premium — $202.90 a month in 2026. IRMAA is an extra amount stacked on top of that (and on top of your Part D premium) once your income crosses a threshold. Instead of the government covering its usual ~75% of your Part B cost, higher-income beneficiaries pay a larger share — 35%, 50%, 65%, 80%, or 85% of the total, depending on which tier you land in. The higher your income, the bigger the surcharge.
The two-year lookback
This is the part that blindsides people. IRMAA isn't based on this year's income — it's based on your tax return from two years ago. Your 2026 surcharge is generally set by the return filed in 2025 for tax year 2024. So a one-time spike back then — selling a house, a big Roth conversion, a year with extra capital gains — can drive a surcharge today, even if your income has since dropped back to normal.
What counts as income (MAGI)
IRMAA uses your MAGI — and the official definition is broader than the income you pay tax on. In SSA's words, your MAGI is your adjusted gross income plus your tax-exempt interest income. That matters:
- Tax-exempt (muni-bond) interest still counts. You can owe zero income tax on it and still have it push you over an IRMAA line.
- Capital gains — from selling a home or stock — flow in.
- Traditional IRA and 401(k) withdrawals count.
- Roth conversions count in the year you convert.
The lesson: the income that triggers IRMAA is wider than your taxable income. Knowing what's in that bucket is step one to staying under a line.
Why it's a cliff, not a slope
IRMAA doesn't phase in gradually. It's a cliff: one dollar over a threshold moves you into the whole next tier and the full higher surcharge — for the entire year, on both Part B and Part D. That's why planning around the lines matters so much; a tiny overage can cost real money that a little timing would have avoided.
How to appeal it — Form SSA-44
If your income fell because of a life-changing event — retirement or work stoppage, loss of a pension, the death of a spouse, or divorce — you don't have to accept a surcharge built on your old, higher income. File Form SSA-44 and ask Social Security to use your current income instead. Going forward, you can also manage MAGI on purpose: spread big withdrawals across years and keep Roth conversions sized to stay under a bracket line.
Clear the noise — go to the source
The brackets change every year, so check the current figures at the source rather than trusting a stale number. Handle everything at medicare.gov and ssa.gov — never a middleman who found you first. If a pitch makes you feel panic or reach for your wallet, that's your signal it's bait.
Free 1-page "IRMAA Cliff" cheat sheet
The 2026 brackets, exactly what counts toward MAGI, the two-year lookback, and the SSA-44 appeal — on a single page.
Get the cheat sheet→Sources
• Medicare.gov — Medicare costs 2026 (standard Part B $202.90, deductible $283)
• SSA — Medicare Premiums: Rules for Higher-Income Beneficiaries (2026 IRMAA brackets + MAGI)
• SSA — Form SSA-44 (Medicare IRMAA — Life-Changing Event)
Common questions
What income does IRMAA use?
IRMAA uses your MAGI — your adjusted gross income plus any tax-exempt interest income. Tax-exempt muni-bond interest still counts. Capital gains, traditional IRA withdrawals, and Roth conversions all flow into it, so the income that triggers IRMAA is broader than the income you pay tax on.
Why is my 2026 Medicare premium based on old income?
IRMAA runs on a two-year lookback. Your 2026 surcharge is generally set by the tax return filed in 2025 for tax year 2024. A one-time 2024 income spike — a home sale or a big Roth conversion — can raise your 2026 premium even if your income has since dropped.
How do I appeal or lower IRMAA?
If your income fell because of a life-changing event — retirement, work stoppage, loss of a pension, death of a spouse, or divorce — file Form SSA-44 to have Social Security use your current, lower income instead of the two-year-old return. You can also manage future MAGI by spreading out withdrawals and keeping Roth conversions under a bracket line.