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 proposal should have nine main parts and it should be around six to ten Pages for smaller deals below ten thousand dollars for bigger Enterprise deals.To write a proposal letter, follow these simple steps. Alongside our guidelines, we also offer proposal letter templates and examples. Read our article on the five steps for writing a business proposal letter and get a free template with top examples of successful letters. How do you write a business proposal letter? Do not simply make a general reference to any other document included with the Proposal. This hearing is in a hybrid format. Acknowledged in the proposal. Women Business Enterprise (WBE), and Veteran Business Enterprise (VBE).