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)