When processing medical billing for hospitals, location of services is everything and you must be certain that the correct place of service coding is used. That is where code 21 comes in handy. Place of service code 21 is used in medical billing for all inpatient hospital care. Admittance of a patient to the hospital will make it necessary to use the inpatient hospital POS code 21. Many medical billers get confused when the emergency department comes into play. They question whether or not they should use place of service code 23 for emergency room-hospital, or place of service 21 for inpatient hospital if a patient is admitted from the …