There are different types of proposals, but the two most common are business proposals and project proposals. A business proposal is sent to a potential or current client in order to obtain a specific job. A project or research proposal details a project you plan to undertake in order to solve a problem or prove a hypothesis.
The conclusion of any good piece of writing is a restatement of the central idea, a final chord at the end of a persuasive song. A conclusion is one paragraph in length and along with a restatement of the proposal's main idea includes a call to action. A proposal is used to convince the reader to greenlight a project or plan. At the end of a good proposal, you're asking the reader to do just that, to say yes to your proposed idea.
Example of a Business Proposal Conclusion
Let's say you work for a technology firm and you've written a proposal to a prospective client outlining why they should install your security software. You've already stated why this software is a good fit for their business along with the cost, timeline for installation and other important details. Now for the conclusion. It might go something like this:
Securing your data is the most important step you can take as a business owner, and I think you'll agree that the value this security software will add to your company is priceless. Please contact us at your earliest convenience to set up a consultation so we can get started securing your company's information as soon as possible.
The first sentence is a restatement of the proposal's main idea, and the second sentence is a call for immediate action.
Example of a Conclusion for a Project Proposal
The conclusion of a project proposal should do the same thing it does for a business proposal, but the information and tone will be different. Any type of academic writing is much more formal than the tone you'll typically find in a business proposal, which usually gets straight to the point in the clearest language possible.
In your final paragraph, you will summarize the project including the problem, motivation and proposed solution. Then you will include a call to action, which in this case will mean green-lighting the project or providing funding.
As an example, let's say you've written a proposal to study the effectiveness of a new type of solar panel that can be used in colder, cloudier climates.
The primary goal of this project is to prove the efficacy of these new solar panels in cool and cloudy climates. Solar panels work well in sunny locations, but up to this point they have proven ineffective in other types of climates. These newly engineered panels will be tested in four locations and data will be gathered to determine their success. We need to initiate the program by October 1 in order to accurately test the panels, and your funding and support for this project are essential.
Note the more academic tone and more detailed explanation found in this type of proposal. However, it accomplishes the same goals: restating the main idea of the proposal as well as a call to action.