Coordination of Benefits (COB) is a provision in most health plans that allows families with two wage earners covered by health benefit plans to receive up to 100% coverage for medical services. COB rules determine which plan is primary for you, your spouse and your dependent children. Under COB your plan is primary for you, and your spouse's plan is primary for him or her, and the "Birthday Rule" determines children's primary coverage.

How it Works

First, the primary plan pays your claims as if there were no other insurance. Then your spouse's plan pays for what your plan did not, providing it is a covered benefit. For example, if your doctor's visit costs $80 and your health plan, which is primary, pays $50 of that, your secondary health plan could pay the remaining $30. Remember, the claim must be considered a covered expense by your spouse's plan.

COB is an industry standard that was created by the National Association of Insurance Commissioners (NAIC) in conjunction with the insurance industry. It is not a law. COB can be complicated, especially if you and your spouse have different plan types, for instance, if you have a PPO type plan and your spouse has an HMO. Here is how COB generally works when you and your spouse are covered under each other's health plan:

• The plans will not pay more than 100% of the cost of the medical treatment, nor will either pay for a treatment or service not coverend under that plan.
• In determining which plan is primary and which is secondary, a plan without a COB provision is generally considered primary.
• When both have COB rules, the plan in which you are enrolled as an employee or as the main policyholder is primary. The plan in which you are enrolled as a dependent--your spouse's plan--would be secondary.
• In addition, if you have COBRA coverage as well as coverage with another plan in which you are enrolled through an employer, your COBRA plan is secondary and your employer's plan is primary.
• The "Birthday Rule" applies only to children.
• If none of the above provisions determines which plan is primary, the plan covering you the longest is typically considered primary (although some insurers might say the claims are shared equally by both plans).