Project management is naturally complicated, but it can be disastrous if you don’t have sufficient buy-in from the right parties. Writing a strong and complete business case can make all the difference.
A business case is intended to convince key decision-makers of the merits of a particular course of action.
It is a key part of your project documentation: if a project brief describes what needs doing, and a project plan explains how, the business case sets out why.
A good business case will explain the problem, identify all the possible options to address it, and allow decision-makers to decide which course of action will be best for the organisation.