Pre-contractual referral: an unauthorized variant makes the offer irregular!
Reminder # 1:
One variant consists of a modification of certain specifications of the services described in the consultation file with a view to presenting more interesting financial proposals or technical proposals that are more efficient than those that could result from the basic offer alone.
The variants are left to the free initiative of the candidates and can not be imposed by the contracting authority. Clearly, a mandatory variant is not a variant but an option.
The contracting authority must very precisely indicate the elements of the specifications on which candidates are authorized to submit variants.