Anything that is done repeatedly, or by more than one person in your company, should be documented. You may have started out by “having everything in your head,” but when you begin delegating to employees, you need to ensure that they will be able to replicate your processes in order to provide the same level of service to your customers.
Your employees may have their own processes for getting things done, but what happens if they should leave the company? Or even just go on vacation?
Have your processes professionally documented with tutorials, user guides, or reference manuals. This can make the difference between a business that plods along with a business owner constantly on the verge of burnout, and one that is successful.