Cal. Rev. & Tax. Code § 2195

Thirty years after any tax becomes a lien, if the lien has not been otherwise removed, the lien ceases to exist and the tax is conclusively presumed to be paid. The official having charge of the records of the tax shall mark it “Conclusively presumed paid.” Property for which a power to sell has been recorded for nonpayment of taxes is not subject to the provisions of this section.