Start by writing a description of your business, including what stage of development it is currently in (conception, start_up, first year, mature, exit) and your plans for growth. Discuss the nature of your business, the main products and services you offer, the market for your products and services, and how and by whom the business is operated.
The organizational section of the business plan also needs to include an explanation of your record keeping process, checks and balances, and control management systems. Anyone who reads your business plan should be able to understand the organizational procedures for running your business day_to_day, as well as in an emergency situation.
For an online business, a detailed and in depth business plan is usually not necessary unless you are trying to combine your online business with a traditional business. For most online business startups, the detail involved with planning a traditional business is not required. However, it would still be beneficial to you if most of the topics were still covered, even if only briefly. Having a written plan in front of you will help you to focus on important aspects of the business.
You may not have thought much about your competition or outsourcing some of your work, but things like that will impact your ability to make a profit. And you will find this especially so in the beginning phases of your business. Even you are just opening a lemonade stand in the front yard, you will still need to know what Susie is selling her lemonade for on the next street over!