|You can boast to all the world that Tom Cruise told you over lunch that he'd love to be in your film, but nobody will believe you if you don't have a written statement from him to back it up.|
During preproduction, a great asset to have is a letter of intent from a significant actor or technician. It's an informal letter (or, in this case, a fax) stating that person's interest in working on the film. Although not legally binding, it's extremely helpful in getting other people interested in working on the film or investing. It adds a lot of credibility to your production. "Gee," others say. "Some cool people want to work on this film. Maybe I should too."
Mel was gracious enough to fax me this kind statement just one month before filming began. Usually letters of intent are sent out much earlier, to help spark financial backing when all a filmmaker has is the script or general idea.
I didn't have to get any letters from any of the other actors, as they came in to audition personally. Once their agents were told that we were interested in working with them, my producer and casting director drafted up deal memos for each actor. Still not legally binding, a deal memo falls somewhere in between the letter of intent and the actual formal contract.