Rev. & Tax. Code, § 3706

If the property is not redeemed before the close of business on the last business day prior to the date of the sale of the property, the tax collector shall sell the property at public auction to the highest bidder at the time and place fixed.

In the case of a sale at public auction, no bid shall be accepted for a sum less than the minimum price approved in the resolution of the board of supervisors; provided, however, the tax collector may reduce the minimum price under any of the following circumstances:

(a) If a partial redemption has been made under Chapter 2 (commencing with Section 4131) of Part 7 of Division 1.

(b) If a partial cancellation has been made under Chapter 4 (commencing with Section 4985) of Part 9 of Division 1 after that price was fixed, by not more than the ratio that the delinquency on the portion so redeemed or canceled bears to the delinquency upon the whole.

(c) If the total amount necessary to redeem is decreased due to the removal or reduction of default taxes resulting from the removal or reduction of a special assessment or a direct charge against the property.