This website has a great example of a business letter format. Finally, remember your goal.In this article, we discuss how to write a business proposal letter and we offer sample letters and templates you can use as a guide. A business proposal is a document that outlines a specific product, service, or project that a company offers to potential clients or partners. We'll outline basic formatting techniques that can be used thoughtfully and strategically to strengthen your proposal. Make sure that you refer to the Proposal Submission. In this article, we explain how to write a business proposal letter and examine a few sample letters. We have reviewed ten of the best proposal templates we could find online across various industries. These proposals showcase multiple proposal formats. A business proposal letter is a document sent to a prospective client or partner, introducing your services or requesting an opportunity.