California Code, Revenue and Taxation Code - RTC § 4531

(a) A holder of a tax certificate may apply to the tax collector for a duplicate certificate if the original certificate has been lost or destroyed.  The tax certificate holder shall give an affidavit to the tax collector stating that the affiant is the owner of the tax certificate and that the tax certificate was lost or destroyed.  The tax certificate holder shall pay a fee for the issuance of the duplicated tax certificate in an amount as determined by the tax collector.

(b) The tax collector shall issue a duplicate tax certificate, and shall plainly mark or stamp that tax certificate as a duplicate, and enter the fact of the duplicate in the tax certificate record opposite the entry of the sale for which the lost or destroyed tax certificate was issued.  He or she shall enter in the same place a notation of the alleged loss or destruction, whether or not the duplicate certificate is issued.