Cal. Sts. & High. Code § 6516

Upon production by the holder of the certificate of sale of the official receipt for the amounts so paid by him, the treasurer shall make an indorsement upon the certificate of sale showing that receipts have been so produced and stating the nature of the tax or lien paid, and the amount thereof. He shall also make a like entry in the book containing the bond record and shall collect the amount so entered as a part of the amount represented by the certificate of sale together with interest thereon at the same rate as provided on the purchase money for redemption.