California Code, Revenue and Taxation Code - RTC § 4505

(a) A tax certificate shall be issued for a separately assessed parcel, or for multiple parcels with separate assessments, that are delinquent or defaulted at the time of the offer of the sale of the tax certificate and not for any subsequent year taxes or assessments. A tax certificate shall identify the parcel or parcels securing the certificate, bear the date of the purchase of the tax certificate, the name of the purchaser (or any successor) of the tax certificate, the total amount due, including taxes and assessments, being assigned to the purchaser of the tax certificate (as they may be reduced pursuant to subdivision (b) of Section 4525), and the purchase price of the tax certificate.

(b) Tax certificates may be in the form of physical certificates or may be in book-entry form, including an electronic medium, in the discretion of the county.