Retract a bid on eBay by filling out the Bid Retraction Form. Enter the item number for the relevant auction and a reason for retracting the bid. The retraction request may not be accepted depending on the reason. Some examples of acceptable reasons are accidentally entering an incorrect bid amount, the item description changing significantly after the initial bid, or being unable to authenticate the seller's identity.
According to eBay, retractions are generally only accepted if the bid was placed when the auction was more than 12 hours from closing or if the bid was made less than one hour prior to the request. In the event that the seller materially changes the item description, a retraction request may be made at any time.
Some examples of circumstances under which a bid retraction request would be denied are the bidder changing his mind about buying the item, the bidder deciding she can't afford the item, or the bidder placing a bid higher than he initially promised himself he would go.
The number of bid retractions in the last six months is recorded in each buyer's feedback profile, which is visible to sellers.
A bidder may also ask a seller to cancel a bid at any time. Whether to do so is completely at the discretion of the seller.