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
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, 80% for level 4, and 85% for level 5.