How does coordination of benefits (COB) determine which payer pays first?

• A. Randomly chosen by the insurer.
• B. By policy rules that assign primary vs secondary payer status based on plan type and enrollment.
• C. By patient preference.
• D. By the provider's determination.

Answer: (B)

Coordination of benefits uses each plan’s rules to decide who pays first. Each policy defines a primary payer and a secondary payer based on plan type and how you’re enrolled. In practice, the plan that covers you as your main policy (often an employer-sponsored plan for the employee) pays first, and the other plan pays remaining eligible charges according to its own benefits. This keeps from paying the same costs twice and ensures benefits are coordinated across policies. It’s not random, not based on patient preference, and not determined by the provider; it’s set by the contracts and enrollment status.