If you're going to do fixed price, you really need a proper spec, change management process and approval process defined up-front. If the project isn't large en

If you're going to do fixed price, you really need a proper spec, change management process and approval process defined up-front. If the project isn't large enough to justify that or the participants aren't willing to do it, going fixed price is almost inevitably going to cause problems. On the other hand, if you do have a reasonably clear idea of what you want up front as the client, and if you do have a reasonably clear idea of what it will take to achieve that as the service provider, a fixed-price contract on reasonable terms can work to both parties' advantage. The client gets a degree of certainty from early on that they would not have with time-based pricing. The service provider assumes the risk but is better able to judge it, and can price based on the value they are offering to the client and the degree of risk involved, potentially increasing their margin considerably while still having happy clients.