The purpose of the income-related monthly adjustment amount is to reduce the Federal subsidy of the Medicare Part B program for beneficiaries with modified adjusted gross income above an established threshold. These beneficiaries will pay a greater share of actual program costs. Medicare Part B premiums paid by beneficiaries cover approximately 25 percent of total Medicare Part B program costs and the remaining 75 percent of program costs are subsidized by the Federal Government's contributions to the Federal Supplementary Medical Insurance Trust Fund. The reduction in the Medicare Part B premium subsidy results in an increase in the total amount that affected beneficiaries pay for Medicare Part B coverage. A beneficiary with modified adjusted gross income above the threshold amount will pay:

The Medicare Part B standard monthly premium; plus

Any applicable increase in the standard monthly premium for late enrollment or reenrollment; plus

An income-related monthly adjustment amount.

The Centers for Medicare & Medicaid Services (CMS) in the Department of Health and Human Services (HHS) publishes the Medicare Part B standard monthly premium each year. CMS also establishes rules for entitlement to a nonstandard premium, as well as premium penalties for late enrollment or reenrollment (42 CFR 408.20 through 408.27).

We use information that we get from IRS to determine if beneficiaries who are enrolled in Medicare Part B are required to pay an income-related monthly adjustment amount. We also change income-related monthly adjustment amount determinations using information provided by a beneficiary under certain circumstances. In addition, we notify beneficiaries when the social security benefit amounts they receive will change based on our income-related monthly adjustment amount determination.