In some cases, despite multiple bids being received, there may not be a clear preferred bidder. For example, this could be because no bids conform to requirements; or because a non-conforming bid appears to present a better value-for-money option than conforming bids.
One common cause of this problem is poor clarity or quality of the RFP documents-the references listed above under 'Preparing and issuing Request for Proposal documents' provide guidance on preparing a clear, comprehensive, and well-structured RFP, to avoid this issue. The multi-stage and competitive dialogue procedures described in 3.5.1: Deciding the Procurement Strategy also help avoid this issue, by enabling changes to the RFP during the bid process that help ensure final bids are all comparable and compliant.
One option if no bids conform, and none appear to be of high quality, is simply to re-package and re-tender the project. The alternative is to extend the procurement process, to identify a preferred bidder: typically through discussions with the higher-ranked bidders on the points where the bids do not conform, often followed by asking for a revised bid.
For further guidance, see Australia's National PPP Practitioners' Guide [#16, pages 27-28], which describes two options in cases where no preferred bidder can be selected-entering into a 'Best and Final Offer' (BAFO) process with two bidders, or structured negotiations. The South Africa PPP Manual Module 5 [#219, pages 51-56] also describes in detail when and how to run a BAFO process, if no clear preferred bidder can be identified.