A project proposal budget is a financial document that outlines the estimated costs of a proposed project. It contains details such as materials, services, labor costs, anticipated expenses, and any other potential costs associated with beginning and completing a project. By providing an accurate cost estimate for a project, a project proposal budget allows companies to make smarter business decisions about whether or not to pursue a certain project. A project proposal budget also serves as a roadmap, helping to guide the progress of a project from idea to completion.