Income-Related Monthly Adjustment Amount
IRMAA is a surcharge added to Medicare Part B and Part D premiums for higher-income beneficiaries, calculated using income reported on a tax return from two years earlier rather than current income.
Medicare looks backward two tax years to decide what you pay today — a big income event two years ago can raise your premium now, even if that money is long gone.
Go deeper on how this actually works and how it's used.