According to Tech Republic, writing an informal proposal involves applying a less strict format to the structure of a formal proposal, as the contents of the informal proposal is usually derived from the main components of the formal proposal. An example of an informal proposal is a summary of several meetings held with a client.
An informal letter of proposal works well when following up several meetings with clients, and they usually contain an explanation of the writer's qualifications and his proposed solutions. The informal proposal typically does not contain as many graphics as the formal proposal and does not go into extensive details in the cost analysis section; a price range may be suggested rather than a fixed price.
According to Virginia Tech, an informal proposal may include sections such as the introduction, discussion, resources, costs and conclusion. The introduction normally covers the purpose, the problem statement, the background and the scope of the project. The discussion section usually covers the planned approach, the intended result and the statement of work. The resources section includes the personnel, facilities and equipment. The costs section covers the budget and the project time line, while the conclusion discusses the benefits or risks of the proposed solution.