Creating a business that can succeed financially is a massive challenge regardless of whether it is a social enterprise or a regular profit making business. In the past 10 years there has been a revolution in the way we approach starting businesses. Customer driven approaches like Lean Startup allow us to take a new business idea and test out whether it is likely to succeed before we commit large amounts of time and money to the idea. The Social Lean Canvas gives us a format to apply the rigour of lean startup to social enterprise ideas. Through this approach we can reduce the costs of testing new ideas, reduce the time it takes to develop them and ultimately reduce the risk of failure. The canvas is a template that allows us to quickly capture all of the crucial components of a business model on a single sheet of paper. In this form it is easy to work out where the big risks in the proposed business model are and devise tests that will prove the business model to be either viable or not before we commit ourselves to building it. Evolving out of the tech startup space, this iterative customer driven approach is especially powerful for testing out innovative or disruptive ideas but is quickly becoming best practice for testing all new business ideas. In this workshop we will be working through the fundamentals of how lean startup works with social enterprise as well as the social lean canvas itself, why it is valuable as well as when and how to use it.