Cal. Rev. & Tax. Code § 4528

(a)
1. (1) The tax collector may sell tax certificates by any form of public or private sale, including, but not limited to, an auction, a negotiated sale, or a bulk sale. Except as provided in subdivision (c), the price received for a tax certificate shall not be less than the amount of taxes and assessments being assigned thereby. Prior to any sale of any tax certificates, the tax collector shall do all of the following:
  1. (A) Determine the size of the offering and the parcels to be included in the sale.
  2. (B) Determine the fees necessary to conduct the sale and maintain adequate tax certificate records.
  3. (C) Establish rules and procedures for the making of offers on any tax certificate.
  4. (D) Publish the determinations, fees, rules, and procedures described in this paragraph.
  5. (E) Make these determinations, fees, rules, and procedures available to any person upon request.
2. (2) The tax collector has the right to accept or reject any or all bids in his or her sole discretion, subject to the determinations, fees, rules, and procedures described in paragraph (1).
(b) Except as provided in subdivision (c), the tax collector may not sell a tax certificate if any of the following apply:
1. (1) The parcel is not on the secured roll or supplemental roll.
2. (2) The parcel is owned by a governmental agency.
3. (3) The total amount of taxes and assessments to be assigned thereby is less than one hundred dollars ($100), unless the parcel is included in a bulk sale.
4. (4) The parcel has a recorded public notice concerning pollution or contamination to the degree that the parcel poses a public health concern or environmental hazard.
5. (5) The parcel was subject to a proceeding in federal bankruptcy court prior to the sale of the tax certificate.
6. (6) The parcel was subject to any condemnation proceedings prior to the sale of the tax certificate.
(c) Notwithstanding subdivisions (a) and (b), the tax collector may sell or resell tax certificates for parcels described in paragraphs (3), (4), (5), and (6) of subdivision (b), any certificate subject to the Sailors and Soldiers Relief Act, and for parcels described in paragraph (5) of subdivision (a) of Section 4527, at a discount, in accordance with the determinations, fees, rules, and procedures published by the tax collector.
(d) If, pursuant to Section 4521, the tax collector is required to offer for sale a tax certificate for which there exists an outstanding tax certificate for the assignment of taxes and assessments for a previous year, until the date occurring six months after the date specified in Section 4521, the tax collector shall offer to sell the tax certificate to the holder of the outstanding tax certificate. The tax collector shall notify the holder of the outstanding tax certificate by certified mail of the default requiring the issuance of an additional tax certificate with respect to the same parcel, and of the tax certificate holder’s right, until the date one month after the receipt of this notice, to purchase the additional certificate on the same terms as the outstanding certificate. In addition, the holder of the outstanding tax certificate shall have the right of first refusal to purchase the tax certificate with respect to the same parcel at the highest bid amount until all tax certificates with respect to that parcel are redeemed or canceled. During the six-month period, at the option of the holder of the most recently issued outstanding tax certificate, the tax collector shall sell the tax certificate to the holder of the outstanding tax certificate on the same terms as that outstanding tax certificate.