I have had Health Net private insurance policy for over 8 yrs. I also have a Blue Shield policy that my significant other gets through his work. Health Net has always been my insurance carrier. They are now saying that they are the second carrier and refusing to pay for some items that they have always paid for in the past. Whose decision is it to determine which carrier is the first or second. I pay a full monthly payment for both insurers.

If X and Y are listed as married or domestic partners on both policies, some rules are needed so both don't pay in full. To eliminate having people profit from an illness -- so that policy 1 does not pay 80% and policy 2 also paying 80% and the person pockets 60% the policies put limit on benefits and also square away which of the 2 companies pays. Each policy has language on "coordination of benefits" that determines which of 2 applicable policies is primary and which is secondary. Often there is a "birthday rule" -- read both your policies.