If you have more than one health insurance plan, it is important to understand how your plans work together to pay for your health care. This is called “coordination of benefits” (COB). Generally, one plan is going to pay first (the “primary payer”), and the second plan may pay an additional amount if the primary payer did not cover the entire bill. Some people may have coverage from three health insurance plans, in which case there may be a third or “tertiary payer.” This Quick Guide provides an overview of how different plans may work together to pay for your health care.

An example:

Maria and William are a married couple with two young children, living in New York. Maria has an individual health insurance plan through her employer. William has health insurance through his employer also, but William has a family plan that covers William, Maria, and their children. Maria’s plan through her own employer is her primary payer and the plan through her husband’s employer is her secondary payer. Maria has surgery and the hospital sends a bill to both insurance companies. The insurance plan through Maria’s employer pays its share of the bill first. Her husband’s plan pays the remainder of the bill.

COB rules vary by state and by insurer. If you are covered by more than one health insurance plan, it is important to:

• Understand which of your plans is primary and which is secondary. You can look at the Evidence of Coverage from each plan to see if there is a COB section. If you can’t find the information, you can contact each of your insurance companies and ask whether they are your primary or secondary payer.
• Let each of your health insurance plans know that you have coverage besides theirs; tell them the name of the other insurance plan and how you have it (e.g., through a spouse’s employer or through your military service.)
• Let each of your health care providers know about all of the insurance plans that you have.

Certain types of health insurance have specific COB rules.