Known as the SRS, a software requirements specification is a document consisting of:

  1. Purpose of the SRS
  2. Intended audience characteristics (end users)
  3. Technical environmental characteristics (operating environment)
  4. Scope
  5. Constraints
  6. Function & non-functional requirements
  7. Use case diagrams
  8. Context diagrams
  9. Data flow diagrams

You also need to discuss methods of collecting data for your project, as well as providing evidence of data collection and design.