Once you've iterated a few times on your Lean Canvas and tested assumptions, you're likely off and running and building your product. Now, as CEO, you can turn your focus to telling the story of your company—the customer, problem, and solution—to your key stakeholders.
In short, you need some kind of a business plan.
The phrase “business plan” conjures images of massive tomes filled with charts and graphs of every variety. Startup business stories come in short bursts rather than dozens of chapters. There are two main constituencies to whom you need to be telling the story at this stage.
First, you need to convince investors to fund the effort. Then you have to articulate how you want your employees to fulfill the problem-solution set you're building so you can start building a company alongside your product. While those stories are similar, they aren't identical. For example, your team is primarily interested in what their work lives are going to look like over the next 18 months, while your investors will want to focus on what the likely return from their investment will be.
These two versions of the story need to be told in two different ways, depending on the audience: 10 to 12 slides for investors and a blueprint document for how you'll execute on that plan—your mission, vision, and values—for the team.
The business plan isn't dead. It's just gotten a lot shorter.