1. With the exception of the case provided for in Article 87(6), in the course of the negotiated procedure, the tenders are evaluated in several stages by the contracting authority:
a) As regards the first tender, not entailing a validity period and submitted within the time limit for submission of tenders set in the invitation to tender, the contracting authority shall verify that the first tender is in compliance with the terms set out in the procurement documents. If the tender is invalid due to a reason in relation to which the tender may not be made suitable in the course of the negotiations or the supply of missing information, the tender shall be declared invalid prior to the starting of the negotiations. Before starting the negotiations, the tender may only be declared invalid due to unsuitability of the professional tender, if the professional tender does not comply with the minimum requirements laid down by the contracting authority. Any other missing data, information in relation to the declarations, documents included in the tender shall be supplied until the conclusion of the negotiations.
b) After the conclusion of the negotiations, the contracting authority shall verify that the final tenders are in compliance with the contents of the procurement documents at the time of the conclusion of the negotiations and with the requirements set out in the relevant legislation, and, where appropriate, he applies Article 72. Any missing data, information in relation to the declarations, documents which should have been supplied until the conclusion of the negotiations on the first tender, may not be supplied subsequently.
c) The final tenders, which are considered suitable according to point (b) shall be evaluated by the contracting authority on the basis of the award criterion set in the notice launching the procedure and, if the certificates have not been requested in an earlier stage of the procedure, the contracting authority shall proceed pursuant to Article 69(4)-(6).