Medicare IRMAA.
A definition, in plain English — with the books that teach it.
What it means
IRMAA (Income-Related Monthly Adjustment Amount) is a surcharge added to standard Medicare Part B and Part D premiums for beneficiaries whose income exceeds certain thresholds. The Social Security Administration determines IRMAA using Modified Adjusted Gross Income (MAGI) from two years prior. There are five income tiers above the base premium threshold, with surcharges ranging from a small addition to several hundred dollars per month. IRMAA is a significant planning consideration for retirees executing Roth conversions, recognizing capital gains, or taking large IRA distributions.
Example
A couple's 2024 MAGI was $250,000 due to a large Roth conversion. In 2026, each spouse pays the IRMAA surcharge — roughly $111/month extra on Part B premiums per person, or $2,664 per year combined — above the standard Part B premium. Planning the conversion in a year with lower income avoids this cliff.