42 CFR § 408.28
Increased premiums due to the income-related monthly adjustment amount (IRMAA)
June 11, 2020
Beginning January 1, 2007, Medicare beneficiaries must pay an income-related monthly adjustment amount in addition to the Part B (SMI) standard monthly premium, plus any applicable increase for late enrollment or reenrollment, if the beneficiary's modified adjusted gross income exceeds the threshold amounts specified in 20 CFR 418.1115.
[73 FR 36469, June 27, 2008]