The Railroad Retirement Board will begin June 1 to withhold from benefits checks premiums for Medicare Part C (Medicare Advantage plans) and Medicare Part D (prescription drug plans).

Withholding is voluntary, and beneficiaries should contact their plans to request withholding by the Railroad Retirement Board of these premiums from their monthly benefits payments.

Part C and Part D premiums vary according to the plan and provider.

Note that a new federal law requires some Part D beneficiaries also to pay an additional monthly adjustment amount, depending on a beneficiary’s or married couple’s modified adjusted gross income.

While the RRB will be able to deduct the regular Part D premiums for individuals who elect to have them withheld from their benefits payments, Part D enrollees subject to the monthly adjustment amount will continue to receive a bill for that portion as the Railroad Retirement Board says it is unable to deduct those amounts from benefits at this time.

The Part D income-related monthly adjustment amounts are $12, $31.10, $50.10 or $69.10, depending on the extent to which an individual beneficiary’s modified adjusted gross income exceeds $85,000, or a married couple’s income exceeds $170,000. The Social Security Administration determines if a monthly adjustment amount is due, based upon the most recent tax return information available from the IRS.

The Railroad Retirement Board also reminds Medicare beneficiaries that the annual enrollment period for Part C and Part D coverage will be between Oct. 15 and Dec. 7 this year, rather than Nov. 15 through Dec. 31, as it was in previous years. Changes and enrollments made during this period will still be effective Jan. 1, 2012.