This bill proposes significant changes to the calculation of income-related monthly adjustment amounts (IRMAA) for Medicare Part B premiums, effective beginning in 2027. It amends Section 1839(i) of the Social Security Act to raise the income thresholds at which beneficiaries are required to pay higher Part B premiums. Specifically, for years starting in 2027, the legislation sets a new base income threshold of $171,000 for single filers, above which IRMAA would apply, representing a substantial increase from current levels. It also introduces a revised structure of income tiers for those subject to IRMAA, with modified adjusted gross incomes between $171,000 and $205,000 incurring 65 percent of the total Part B premium, and higher income brackets paying 80 percent or 85 percent. These adjustments aim to reduce the number of Medicare beneficiaries subject to IRMAA by increasing the income levels at which these additional premiums are assessed.