Can one withdraw their bid legally?
Firstly if the auctioneer has not called “Sold” at the closure of the lot, there is the right to retract that offer. A bidder is able to cancel their offer so long as the hammer has not been put down on the lot.
However once the lot has been closed, if you are the highest bidder and if it has reached reserve, the lot is yours and you legally need to pay for this. There however is no legally binding contract until both the buyer and the seller have signed the contract of sale. There is however no cooling off period once the auction has closed. Non payment of the lot will cause you to loose your deposit for the auction.
However you are protected by the Customer Protection Act in terms of receiving items that are not what was stated on the auctions. For example if you won a 1.6 stated vehicle but when you go to collect, it is a 1.4 vehicle, the bidder is able to rufuse collection and therefore be refunded their payment. However these errors need to be stated in writing so that there is recourse.