Tax
IRMAA
IRMAA is a surcharge added to Medicare Part B and Part D premiums for beneficiaries whose income exceeds a set threshold, determined by a tax return from two years earlier.
Also called income-related monthly adjustment amount · Medicare premium surcharge
The two-year lookback is what makes it a planning issue rather than a billing issue. Income realized in one year sets your Medicare premiums two years later, so a large one-off event (a Roth conversion, a property sale, a business sale) raises a cost that arrives long after the decision.
It also behaves as a cliff rather than a slope: crossing a threshold by a small amount can increase the premium by a full step. That makes the last few thousand dollars of realized income in a year disproportionately expensive, and worth knowing about before December rather than after.
What it does not do
IRMAA is not permanent. It is recalculated annually, so a single high year raises premiums for a limited period rather than for life. It also is not automatic to appeal, but certain life-changing events do allow a reassessment, which is worth knowing if income has dropped since the return being used.
This entry is a general explanation, not advice for your situation, and it deliberately avoids thresholds and figures, because those are the part most likely to be out of date. Reviewed August 27, 2026. If a decision turns on any of it, ring the office rather than relying on a page.
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