What is the purpose of a 'coordination of benefits' (COB) provision when a person is covered by more than one health plan?

A coordination of benefits (COB) provision applies when a person is covered under more than one health plan (for example, their own and a spouse's). COB rules establish which plan is 'primary' (pays first) and which is 'secondary' (pays remaining eligible costs), so that the combined payments do not exceed the actual covered expenses. This prevents the insured from collecting more than 100% of the cost and profiting from having multiple policies, consistent with the principle of indemnity. Understanding that COB coordinates, rather than duplicates, payments among multiple plans is standard policy-provisions content on the health insurance exam.