Short answer: IRMAA is an extra amount higher-income beneficiaries pay on top of their Medicare Part B and Part D premiums. For 2026 it starts when income (from your 2024 tax return) exceeds about $109,000 for individuals or $218,000 for couples.
The Income-Related Monthly Adjustment Amount (IRMAA) raises Part B and Part D premiums for higher earners. Medicare looks back at your modified adjusted gross income from two years prior (2024 income sets 2026 premiums), and once you cross a threshold you pay a surcharge on a sliding scale. For 2026, surcharges begin above roughly $109,000 (single) or $218,000 (married filing jointly), on top of the standard 2026 Part B premium of $202.90. It’s a ‘cliff,’ so going even $1 over a bracket triggers the higher amount, which is why managing taxable income in retirement matters. If your income dropped after a life event (like retirement), you can appeal using Form SSA-44.