Cal. PROB § 19151

(a) A claim shall be supported by the affidavit of the creditor or the person on behalf of the claimant stating: (1) The claim is a just claim. (2) If the claim is due, the facts supporting the claim, the amount of the claim, and that all payments on and offsets to the claim have been credited. (3) If the claim is not due or contingent, or the amount is not yet ascertainable, the facts supporting the claim. (4) If the affidavit is made by a person other than the creditor, the reason it is not made by the creditor. (b) The trustee may require satisfactory vouchers or proof to be produced to support the claim. An original voucher may be withdrawn after a copy is provided. If a copy is provided, the copy shall be attached to the claim.