There are a number of reasons why you need a plan:

  1. You need to convince others, typically providers of finance (business angels, venture capitalists, banks, investors) or providers of other resources (R&D money, people), or even future staff!
  2. You need a roadmap for yourself and the company, to align and focus your efforts on a clearly articulated plan.  If you don’t know where you are going, any road will take you there.  As the Chines proverb says: “Failing to plan is planning to fail”