If a homeless patient is living somewhere such as doubled up, in a shelter, transitional housing, or other locations for which a ZIP code can be obtained, that ZIP Code is used. Other homeless patients, especially those living on the street, do not know or will not share an exact location. When a ZIP code location cannot be obtained, or the location offered is questionable, health centers should use the ZIP code of the location where the patient is being served as a proxy. Similarly, if the patient has no other ZIP code and receives services in a mobile van, the ZIP code of the location where the van was parked that day should be used. Health centers might collect the address of a contact person to facilitate communication with the patient; however, while appropriate from a clinical and service delivery perspective, this contact address is not to be used as the address for the patient.