Once you make a bid on an item on eBay is it possible to opt out even if you are the highest bidder?

Generally, you cannot opt out after you have placed a bid on an eBay item. This is because all bids that you make are binding; that is, if you win an item, you have to pay for it, even if you've changed your mind.

There are only a few exceptions where you can legitimately withdraw your bid and these are:

if you cannot contact the seller

if the seller changes the listing after you have placed your bid

if you accidentally bid the wrong amount (although in this case you need to bid again straightway but entering the correct amount)

If you do win an item and do not pay for it, the seller will almost certainly open a case against you. This is because eBay charge the seller a fee for the sale, even if you do not pay, and the only way for the seller to recoup that fee from eBay is for them to open a case against you. When the case is closed (assuming that you still haven't paid) you will have a non-paying strike on your account.