California Code, Family Code - FAM § 5602

(a) An obligee other than the local child support agency may register an order issued in this state using the same procedures specified in subdivision (a) of Section 5601, except that the obligee shall prepare and file the statement of registration.  The statement shall be verified and signed by the obligee showing the mailing address of the obligee, the last known place of residence or mailing address of the obligor, and a list of other states and counties in California in which, to the obligee's knowledge, the original order of support and any modifications are registered.

(b) Upon receipt of the documents described in subdivision (a) of Section 5601, the clerk of the court shall file them without payment of a filing fee or other cost to the obligee.  The filing constitutes registration under this chapter.

(c) Promptly upon registration, the clerk of the court shall send, by any form of mail requiring a return receipt from the addressee only, to the obligor at the address given a notice of the registration with a copy of the registered support order and the post office address of the obligee.  Proof shall be made to the satisfaction of the court that the obligor personally received the notice of registration by mail or other method of service.  A return receipt signed by the obligor shall be satisfactory evidence of personal receipt.