Notify stakeholders of project progress at regular intervals and gain their approval for any changes that substantially impact the deadline, budget or deliverables. Once the final product has been fully tested, staff have been trained (where necessary) and the stakeholders have signed-off the project then it can be implemented in the working environment.
The business requirements document should accurately, and in detail, describe the purpose of the project. It states what is needed to achieve that goal i.e. what is in-scope, what is out-of-scope, any assumptions that have been made, any constraints that have been imposed and expected timescales.