A proposal is just a frothy, glossy sales brochure that no one wants to make or read. A statement of work is the straightforward form of the proposal that describes the work to be done. The statement of work serves as a contract between you and your client. It sets out the responsibilities of each party and in particular identifies which party is responsible for designing any interfaces. The statement of work becomes the contract that binds you and your client together. You can't change it without the consent of the other party. So if you want to include some extra fees on top, do it when you send the first draft of the statement of work. If the client accepts your proposal, then there's no need to include these additional fees in the final agreement. However, if they don't accept it, then you'll have to include them in order to get their business. There are two types of statements of work: fixed-price and time-and-materials. With a fixed-price agreement, you are paid a set amount for a specific job. If you complete the project ahead of schedule, you will be compensated for the extra hours. If the project takes longer than expected, you and your client may choose to extend the time limit for a further fee.