In a 363 auction a type of break-up fee that the debtor agrees to pay to an initial proposed purchaser (the stalking horse) if the proposed purchaser is not the prevailing bidder in the auction. A topping fee is calculated as a percentage of the difference between the stalking horse’s initial offer and the final bid price paid for the assets.
See also 363 Auction, 363 Sale, Bid Protections, Break-Up Fee, Stalking Horse.