How to change your maximum bid

In a live auction:

You can reduce the amount of your maximum bid as much as you like before the auction takes place. If you have changed your mind, all you have to do is go to the lot detail page of the relevant lot and edit the Maximum Bid there.

In a time-limited auction:

You can reduce the amount of your Maximum Bid on the corresponding Lot Detail page, but only up to the current price.