Also, as I understand here are the golden rules for payment posting. Please correct if I misunderstood any of the points:

1 Never keep any overpayment, call ins. if they donot coordinate benefit, pay patient, if pt. is not found, pay the state appropriate dept.

2 If overpaying ins. has other outstanding balances, write a letter stating so and then keep the money if they don't pay for outstanding balance, applying the overpmt to the unpaid balance.