IRMAA

Income-Related Monthly Adjustment Amount: a surcharge Medicare adds to Part B and Part D premiums when your modified adjusted gross income (MAGI) exceeds one of six brackets. About 8 percent of beneficiaries pay it in any year. Brackets are set every fall by CMS. The 2026 thresholds use 2024 MAGI from your federal tax return. The surcharge is a per-month dollar amount, not a percentage. Tier 1 adds $74.10 to Part B and $14.10 to Part D; Tier 5 adds $444.90 and $88.30. Cross a bracket by one dollar and you pay the full surcharge for the entire year.