Cal. Civ. Proc. Code § 873.740

(a) If at the hearing under Section 873.730 a responsible bidder makes a written increased offer that exceeds the sale price by at least 10 percent on the first ten thousand dollars ($10,000) and 5 percent on the amount in excess thereof, the court in its discretion may do either of the following:
1. (1) Vacate the sale and direct that a new sale be made.
2. (2) Vacate the sale, accept the increased offer, and confirm the sale to the offerer.
(b) Except as provided in subdivision (c), the amount by which an increased offer exceeds the sale price is determined on the basis of the gross amount of the increased offer including any commission on the increased offer to which an agent may be entitled.
(c) Where in advance of sale the court has so ordered or the parties have so agreed, if an increased offer is made by a party to the action who is not represented by an agent, the amount by which an increased offer of a nonparty exceeds the sale price is determined on the basis of the net amount of the increased offer excluding any commission on the increased offer to which an agent may be entitled.