A call for bids, call for tenders or invitation to tender (ITT, often called tender for short) is a special procedure for generating competing offers from different bidders looking to obtain an award of business activity in works, supply, or service contracts. They are usually preceded by a pre-qualification questionnaire (PQQ).
Open tenders, open calls for tenders, or advertised tenders are open to all vendors or contractors who can guarantee performance. Restricted tenders, restricted calls for tenders, or invited tenders are only open to selected prequalified vendors or contractors. This may form part of a two-stage process, the first stage of which (as in the expression-of-interest (EOI) tender call) produces a shortlist of suitable vendors.
The reasons for restricted tenders differ in scope and purpose. Restricted tenders can come about because: essentially only one suitable supplier of the services or product exists; of confidentiality issues (such as in military contracts); of the need for expedience (as in emergency situations); of a need to weed out tenderers who do not have the financial or technical capabilities to fulfill the requirements.