The reality is no matter how much you work with things in your head, no matter how confident you may be and how much you think you already have a great vision for your business, there are so many great reasons why you should get it down on paper.
Production/ Operation plan: The production/ Operation plan should include strategies for the following parameters ; Location and reasons for selecting the location ; Physical layout ; Cost and availability of machinery, equipments, raw material ; List of suppliers and, if possible, distributors ; Cost of manufacturing ; Quality management ; Production scheduling, capacity management and inventory management ; Changes in above in the case of expansion of business.
I say that because of course you need to be careful with commercially sensitive ideas, as you do not want to pass your plan on to someone in the pub who then starts your idea before you across the road.
Contextualise Your Budget : Of course your budget will be extremely important. But sometimes people sort of pluck figures out of thin air, not giving it the context it needs in the business plan to make real concrete sense of how that budget is going to work.