42 CFR §408.40

1. (a)Deduction from monthly benefits.
   1. (1)Enrollees who are receiving monthly benefits do not have the option of paying by direct remittance to avoid deduction.
   2. (2)If the enrollee is entitled to more than one type of monthly benefit, the order of priority for deduction is as follows:
      1. (i)Railroad retirement benefits.
      2. (ii)Social security benefits.
      3. (iii)Civil service annuities.
2. (b)Deduction from initial or reinstated benefits. When an enrollee receives a monthly benefit check after an initial award or after a period of suspension, that check is, if administratively feasible, reduced or increased to deduct unpaid premiums or refund premiums paid in advance by direct remittance.
3. (c)Ongoing deductions. The premium for each month is deducted from the cash benefit for the preceding month, e.g., the premium for March is deducted from the benefit for February, which is paid at the beginning of March.