What is the IRMAA (Income-Related Monthly Adjustment Amount)?

IRMAA is an income-based surcharge on Medicare Part B and D premiums for beneficiaries with higher incomes, calculated using tax returns from two years prior. It increases premiums based on Modified Adjusted Gross Income, affecting only Parts B and D, not Part A. Payments are made monthly, with options for automatic deduction or direct payment. Appeals are possible for income changes. Planning income sources, like Roth IRA conversions, can help reduce or avoid IRMAA surcharges.