What is MAGI for Medicare? Medicare uses your Modified Adjusted Gross Income (MAGI), which is your AGI from IRS Form 1040 Line 11 plus any tax-exempt interest income (Line 2a). This includes wages, pensions, RMDs, capital gains, Social Security benefits, and tax-exempt bond interest.

IRMAA cliff warning: Even $1 over a bracket threshold triggers the full surcharge for that tier — potentially $1,000+ more per year. If you're near a boundary, consider income-planning strategies like qualified charitable distributions or Roth conversion timing.