An insurance policy that pays first when a person is covered by more than one
insurance plan (usually associated with health insurance). Each health
insurance policy or plan is called a "payer." When there is more than
one payer, there are "coordination of benefits" rules that decide
which one pays first. The primary payer pays what it owes on an
individual's bills first and then sends the rest to the "secondary
payer" to pay. In some cases, there may also be a third payer.