Authoring project proposals (or project quotations) efficiently and effectively is a critical part of the sales process in every business. The key challenge in the creation of such proposals is capturing the commercial engagement process that took place between two parties (the author of the proposal and the receiver) on a single document that both parties can agree on. The reason this is challenging is that - due to the verbal and non-committal communication leading to the project proposal stage - both parties may have differing perceptions of what has been agreed. In this article, we detail a proven structure that enables to create great project proposals i.e. proposals that establish mutual understanding on why the parties engage (purpose), transparency on what both parties aim to achieve (integrity), and clarity on how both parties' success will be measured and rewarded (trust).