If you use a PO Box, one document must have both the PO Box and physical (residence) address and one document may only contain the PO Box. One document MUST show both your PO Box and physical (residence) address, and one document may show only the PO Box.Box. Check mark the TWO different documents below that you'll use as your proof of California residency. Home utility bill or cellular phone bill (Preferred) No, a P.O. Box does NOT prove residency. You can live in Los Angeles and obtain a P.O. Box in New York City. Proof of a physical address is required. All documents used to establish residency must include: 1. The student's name (or parent's name if student is under 19 and unmarried). Apply at a Post Office: Complete pages 3 and 4 and take this whole form to a Post Office most convenient for you.