After having many meetings to understand the business idea , the most important thing you need to do it to write a professional SRS document , SRS (Software Requirement Specifications) is an essential work product to make sure that the system development will be as expected.
before talking about how to create a professional SRS document , you must know that the Business Analyst is the one responsible for conducting meetings with business owners then create it.
Here are some videos to learn how to write it step by step.
SRS General Components
SRS Stakeholder Register
SRS Definitions & Abbreviations
SRS Introduction Section
SRS High Level Business Requirements
Overall Description Part 1
Overall Description Part 2
SRS System Features