The most flexible, but sometimes complicated, means of procuring goods and services is negotiation. This method is used when contracting offices can't define all the requirements of a procurement, or when factors other than price are important enough to require evaluation.
Negotiated procurements take many forms.
They may call for competitive proposals, may involve restricted competition, or may even be sole source. Some permit discussions with offerors, while others allow award of a contract without discussions. The negotiation procedure permits bargaining between the contracting office and the offerors, who usually are allowed to revise their offers before award of a contract. Contracting officers use negotiated procurements whenever sealed bidding is not appropriate. Generally, negotiation is appropriate if time does not permit sealed bidding, if award will be based on factors other than just price, if discussions are necessary, or if the Government is only aware of one source.