A few years ago, I took on a freelance project to implement an Internet Explorer component in C++. I was billing a healthy hourly rate on other projects at the time, but this particular client insisted on a fixed price. In a bout of temporary insanity, I made an exception and accepted the pre-agreed budget. After all, the project was fairly intriguing and the requirements were straightforward. What could possibly go wrong?

Why We Don't Do Fixed-Price Software Projects (And Neither Should You)