How do you determine coordination of benefits?

Answer:
Standard coordination of benefits goes in the following order for an active employee, not a retiree:

Employee: Policy in which you are the subscriber is the primary. If you are the policyholder on more than one policy, whichever policy has been in effect the longest is primary.

Dependent children: For natural parents still married, or without court order, coordination of benefits follows birthday rule. The parent who's birthday falls first within the year (goes by month, not year) is primary.
For parents with court order, the parent named is primary.
For parents divorced/separated with spouses and no court order, custodial natural parent is primary, then spouse of custodial parent, then non-custodial parent, then spouse of non-custodial parent.

If dependent children are also covered by the state, state health policies always are last in line to pay benefits.

For retirees (65+) still on employer policies and covered by Medicare, Medicare is primary and employer policies are secondary.
Note: There are comments associated with this question. See the discussion page to add to the conversation.
First answer by Guestwork1. Last edit by Sadwinell. Contributor trust: 0 [recommend contributor recommended]. Question popularity: 2 [recommend question].