1. Place of service (POS) where a medical service is performed such as a hospital (inpatient or outpatient), doctor’s office, or skilled nursing facility. When the physician’s office or an outpatient hospital is billing, the two-digit POS code is inserted in Block 24B of the CMS-1500 insurance claim form (e.g., 11 is doctor’s office and 12 is patient’s home). 2. Anatomical location of a medical problem.