which pos to use

Since we don't always know if the hospital has billed as inpt or opt for someone that went through the ER, is there a rule of thumb to use (for POS 21 or 22? Especially if they were there for less than 24 hrs. We have been told that we need to bill the same as the hospital.
Thank you,
Linda

re: which pos to use

There is no rule of thumb, unfortunately. You have to call the hospital or look on line to see the status of the patient.