When the hammer falls on a house auction, the exchange of contract between the seller and buyer of the property becomes legally binding. From this point, the buyer is committed to the purchase; the seller committed to the sale.
The sale completion date will be outlined in the contract, and the parties involved will be required to complete by this date. As a buyer, you are committed to paying the deposit for the property on the date of the auction, followed by the remainder of the full amount by the agreed completion date.