Article R3133-18 of the French Public procurement code
Where an advance payment is made, the period for payment of the advance shall run from:1° The date of notification of the concession contract;2° Where the concession contract so provides, the date of notification of the act by which performance of the services corresponding to the advance payment commences.In other cases, the period for payment shall run from the date on which the conditions laid down in the concession contract…