In the FDD industry there is a practice among a few of those that service PE firms to roll fees rather than make them contingent. The idea being on a dead deal the PE firms pays for professional fees out of pocket versus on a closed deal they get paid by the investors. So on a $75k diligence on a dead deal they'll pay $20-25k to cover the costs but then roll the remaining $50k to the next deal that closes, paying $125k on the next deal if it closes in this example. There is a discussion on whether this is ethical or not, all I'm saying is it's not unheard of happening. On searcher based deals it's difficult to over this rolling service simply because a searcher is rarely closing 3-5 deals a year like a PE fund. The key on getting some kind of terms is volume. Then the risk goes down for all parties as a provider like myself can take a risk on a deal and still have my judgement impaired because I know there will be a lot more coming. So although the success-fee arrangement doesn't work in the space, the volume based pricing does work for PE funds or aggressive purchasers.

For CPAs, contingent fees unfortunately can be seen as creating a conflict of interest under ethics rules; for example, buyside diligence providers who are paid only when deals close may be perceived as motivated to overlook or not report issues they find to their buyer client.