What IRMAA actually is
IRMAA stands for Income-Related Monthly Adjustment Amount, and it’s a surcharge Medicare adds to your Part B and Part D premiums if your income is high enough. For 2026, the standard Part B premium is $202.90 a month. Cross into IRMAA territory and that climbs in steps, all the way to $689.90 a month at the highest tier. Part D carries its own surcharge on top of whatever your drug plan already charges, ranging from $14.50 to $91.00 a month.
The two-year lookback that trips people up
Your 2026 premium isn’t based on your 2026 income — it’s based on your 2024 tax return. That delay is exactly why IRMAA blindsides so many retirees: a big income year from two years ago shows up as a surprise premium increase today, often with no obvious connection in the retiree’s mind between the two. A one-time Roth conversion or a large capital gain from 2024 can still be raising your Medicare bill right now.
Why it’s a cliff, not a slope
For 2026, the first IRMAA tier starts at $109,000 in MAGI for a single filer and $218,000 for a married couple filing jointly. The brackets work nothing like ordinary income tax brackets, where only the income above the line gets taxed at the higher rate. Cross an IRMAA threshold by even a single dollar and the entire surcharge for that tier applies to your full premium — there’s no partial phase-in. Someone with $217,999 in MAGI pays the standard premium; their neighbor at $218,001 pays an extra few thousand dollars a year for both spouses.
How to stay under the line
Roth conversions are best done before Medicare eligibility, or sized carefully if done after, since the converted amount counts fully toward MAGI. Qualified charitable distributions reduce your RMD without adding to MAGI the way a regular withdrawal would. If a specific life event caused your income to drop — retirement, divorce, the death of a spouse — Form SSA-44 lets you appeal an IRMAA determination using your current income instead of the two-year-old figure the SSA would otherwise use. That form is the one tool that works after the fact; everything else has to be planned before the income year closes.
