When does an auction sale officially complete?

An auction sale officially completes when the auctioneer announces it. The authority of the auctioneer is crucial in this process, as they are the designated representative who has the responsibility to conduct the auction and ensure that all proceedings are carried out in accordance with the rules and regulations. The auctioneer's announcement signifies that the bidding has concluded, and the sale is finalized, regardless of whether all items were sold or not.

This moment is critical as it marks the transition of ownership of the items to the highest bidder, thus forming a binding contract. The auctioneer’s announcement signifies that all necessary terms of the auction have been met, including the acknowledgment of the highest bid, which is essential for the culmination of the sale.

Other elements such as the last bid, the number of items sold, or the seller's contract signature might play roles in the overall auction process but do not by themselves signal the official completion of the auction sale. The auctioneer's role is central to the integrity and legality of the auction's conclusion, making this choice the most accurate.