Business case: ("A demonstration that this idea for a new business is a good one.") You must demonstrate how your idea will make money, and where the landmines are that surround you. You are mapping a way to profitability through the minefield. Business case: ("Making your case that buying this thing is a good idea for the company.") How much does the thing cost? How much money does it save, today, in a month, in a year, and over the 3-year life of the thing? Does it save time, as well? Whose time? How much? What could that person/people do with those extra hours you have just saved? That's pretty much it. I do a shitload of this kind of writing, so if you wanna send the thing to me, I'm happy to take a gander and provide edits/comments/feedback.