Can I decrease my proxy bid?
by sir_snipes_alot

Currently it is not possible to decrease your proxy bid amount.

In the process of placing your proxy bid, you were asked to review your bid on the confirmation page - the purpose of this page is to make sure that your bid is accurate and to confirm your intention to commit to the bid at the amount you are entering as your bid. The confirmation page also explains that once a bid is placed it is considered to be a binding contract between the seller and the buyer.

Your question is asked from time to time in the eBay Community Forum on the Bidding Board. There are some who have suggested that this option be made available to bidders.