What is IRMAA and how can higher income raise my Medicare premiums?

IRMAA – the Income-Related Monthly Adjustment Amount – is a surcharge on Medicare Part B and Part D premiums for higher earners. It's based on your modified adjusted gross income from two years earlier, so your 2025 premiums reflect your 2023 tax return. In 2025, the surcharge kicks in above $106,000 for a single filer or $212,000 for a married couple, and it climbs in tiers – the top bracket can add several hundred dollars per month per spouse. Because it's a cliff, earning even one dollar over a threshold can cost thousands a year. That's why retirees watch the size of Roth conversions, capital gains, and RMDs. If a life event like retirement dropped your income, file Form SSA-44 to request a reduction based on current income.