What Is Coordination of Benefits?

Coordination of Benefits (COB) is the process that determines how two health insurance plans share the cost of your care when you're covered by more than one plan at the same time.

When Does This Come Up?

• You're covered by your own employer's plan and your spouse's employer plan
• A child is covered by both parents' plans
• You have employer coverage plus Medicare
• You have a marketplace plan plus Medicaid

Primary vs. Secondary Insurance

One plan is designated "primary" — it pays first. The other is "secondary" — it may pay some or all of what's left over. You can never collect more than 100% of the actual cost of care from both plans combined.

How Plans Determine Who's Primary

• Your own employer plan is primary for you; your spouse's plan is secondary
• For children: the plan of the parent whose birthday comes first in the calendar year is primary (Birthday Rule)
• Medicare coordination follows specific rules depending on employer size

The Potential Benefit

Having two plans can significantly reduce your out-of-pocket costs. The secondary plan may pay your deductible, copays, or coinsurance that the primary plan didn't cover.

What You Need to Do

Notify both insurance companies that you have dual coverage. Provide each insurer with the other plan's information. When you receive care, the provider's billing department handles submitting to both — but make sure they know you have two plans.