The Centers for Medicare & Medicaid Services (CMS) calculates the Medicare Part B
monthly premium amounts and the income-related monthly adjustment amount (IRMAA).
CMS publishes the amounts, which can be found in the current Federal Register each
year. By law, threshold amounts and modified adjusted gross income (MAGI) ranges are
fixed through 2019 and can be found in the same announcement.
For IRMAA beneficiaries, Part B premium surcharges for late enrollment or reenrollment
will continue to be calculated based on the Part B standard monthly premium. More
information regarding Part B premium surcharge calculations can be found in HI 01001.010.
Part B beneficiaries usually pay about 25% of the true cost for Part B. The true cost
of Part B that IRMAA beneficiaries pay is 35% for level 1, 50% for level 2, 65% for
level 3, and 80% for level 4.