Final answer:
The medical assistant should verify the patient's demographic data on each visit for collections control.
Step-by-step explanation:
The medical assistant should verify the patient's demographic data on each visit. This is important for collections control as it ensures accurate billing and minimizes errors. By verifying the patient's demographic data regularly, the medical assistant can update any changes in insurance carriers, address, or contact information, preventing issues with account delinquency or returned statements.