Consequently a, a baseline is usually created when nearing the end of the requirements elicitation phase after stakeholder requests have been reviewed and an initial set of requirements has been create and approved.
A requirements baseline is the set of requirement, source document, and all documents derived from the set of requirement at a specific point in time. If, however, a supplier is receiving the requirements from a customer as part of a negotiated contract, then the set of requirements contained in the contract is normally considered the initial baseline.