Explain your position but do it quickly. The longer you leave it you may get reported for non-paying then eBay give you a black mark and they can suspend your membership, so just be honest. Just say you made a mistake - but I don't understand how you bid - as others say - you have to go through the process. You may be lucky and have an understanding seller, you may not. (I had someone who told me their baby placed the bid without them knowing, yeah right, did they not check your "items I'm bidding on" section?) If you are lucky then someone else may have been bidding and the seller will be able to offer the item to the second bidder - but you won't know until you tell them, Don't delay. If they won't retract then you have to pay, but you can always sell it again on eBay yourself!