From the DOJ web page:
http://caag.state.ca.us/firearms/dlrfaqs.htm#18
33. What documentation is acceptable to demonstrate proof of residency for handgun purchasers?
Under Firearms Division policy and soon to be proposed in regulations, firearms dealers may accept any of the following:
Utility bill reflecting services to a fixed place of residence. ?The utility bill must bear on its face both of the following:
The name of the transferee
Either the residential address declared on the DROS form or the address as it appears on the transferee's identification.
"Utility bill" means any bill by a utility company providing the transferee with direct and exclusive services to the transferee's physical residence whether by a physical connection (i.e., hard wired telephone connection, water or gas pipeline connections, physical gas/fuel delivery to premises) or a fixed antenna telemetry connection for non-mobile reception devices (i.e., radio/video telemetry services transmitted to antenna fixed to the residence).
Residential lease that bears both of the following:
The name of the transferee.
Either the residential address declared by the transferee on the DROS form, or the address as it appears on the transferee's CDL or CID.
"Residential lease" means either: i) A signed and dated contract by which an individual (tenant) agrees to pay a specified sum for the right to occupy an abode for a specified period of time; or ii) A signed and dated rental agreement by which an individual (tenant) agrees to pay a specified sum at fixed intervals for the right to occupy an abode; or iii) A signed, notarized affidavit by a relative that the transferee resides at the relative's abode free of any monetary consideration.
Property deed the bears both of the following:
The name of the transferee.
Either the residential address declared by the transferee on the DROS form, or the address as it appears on the transferee's CDL or CID.
A. "Property deed" means either: i) A copy of a deed of trust, bearing the pertinent county recorder's official seal, of the transferee's property of current residence, naming therein the transferee as a grantee of the trust; or ii) A Certificate of Title officiated and issued by a validly licensed Title Insurance Company bearing the name of the transferee as a title holder to the transferee's property of current residence.
Government-issued (city, county, special district, state or federal) documentation that has all of the following - - This does not include a drivers license or DMV-issued ID card:
The name of the transferee as it appears on the transferee's CDL or CID.
The name of the transferee as the transferee declares on the DROS form.
The residential address of the transferee as it appears on the transferee's CDL or CID or the address update attachment to the driver's license/identification card.
The residential address of the transferee as the transferee declares on the DROS form.
Examples of acceptable proof of residency pursuant to newly-proposed regulations:
DMV registrations are NOW acceptable.
Electricity, gas, cable bill from within the last 3 months.
Signed, dated and notarized rental agreement/contract.
Examples of documents that are NOT acceptable proof of residency:
Hunting or fishing license (these documents are not issued by the government).
Cellular phone bill.
Pay stub.