This variable counts the total number of months during the year when the beneficiary premium was paid by the state. State Medicaid programs can pay Medicare premiums for certain dual eligibles (i.e., for beneficiaries also enrolled in a state Medicaid program); this action is called “buying in” and so this variable is the “buy-in code.” Any month where the BUYINXX variable was: A (Part A state buy-in), B (Part B state buy-in), or C (Part A and Part B state buy-in) is counted.
This variable counts the total number of months during the year when the beneficiary premium was paid by the state. State Medicaid programs can pay Medicare premiums for certain dual eligibles (i.e., for beneficiaries also enrolled in a state Medicaid program); this action is called “buying in” and so this variable is the “buy-in code.” Any month where the BUYINXX variable was: A (Part A state buy-in), B (Part B state buy-in), or C (Part A and Part B state buy-in) is counted.
Source: CMS Common Medicare Environment (CME)