IRMAA for 2024 Medicare Part B and Part D Premiums If you have Medicare Part B and/or Medicare Part D prescription drug coverage, you could owe a monthly surcharge based on an income related monthly adjustment amount (IRMAA.) The IRMAA is calculated on a sliding scale with five income brackets topping out at $500,000 and $750,000 for individual and joint filing, respectively. These figures change annually with inflation. IRMAA calculations have a two-year lag time. Whether you pay an IRMAA in 20