Probably nothing needed. Medicare part B and D premiums are carried to your medical expenses for itemized deduction. If you take the standard deduction, then you are not gaining a deduction so no need to include the reimbursement. If you are itemizing your deductions and are able to take a Medical expenses deduction on Sch A, then you would need to decrease your Medical deduction by the amount of the reimbursement. Some states allow an adjustment to income for health insurance premiums paid. If your state allows this, then you would need to decrease the amount of the health premiums deduction by the amount of the Part B and D reimbursement.
