Contract number: [ complete ]  Contract conditions of December 2015  ‘Irregularity’ : any infringement of a provision of Union and Community law resulting  from an act or omission by an economic operator, which has, or would have, the effect of  prejudicing the Union’s budget.  ‘Notification’  (or ‘notify’): form of communication between the parties made in writing  including by electronic means; ‘Performance of the contract’ : the execution of tasks and delivery of the purchased  supplies by the contractor to the contracting authority; ‘Personnel’ : persons employed directly or indirectly or contracted by the contractor to  perform the contract;  ‘Professional conflicting interest’ : a situation in which the contractor’s previous or  ongoing professional activities affect its capacity to perform the contract to an appropriate  quality standard. ‘Related person’ : any person who has the power to represent the contractor or to take  decisions on its behalf; ‘Substantial error’ : any infringement of a contract provision resulting from an act or  omission, which causes or might cause a loss to the Union’s budget.  ‘Supplier portal’ : the e-PRIOR portal, which allows the contractor to exchange electronic  business documents, such as invoices, through a graphical user interface; its main features  can  be  found  in  the  supplier  portal  overview  document  available  on:  http://ec.europa.eu/dgs/informatics/supplier_portal/doc/um_supplier_portal_overview.pdf II.2. ROLES AND RESPONSIBILITIES IN THE EVENT OF A JOINT TENDER  II.3. SEVERABILITY  II.4. DELIVERY OF SUPPLIES  In the event of a joint tender submitted by a group of economic operators and where the  group does not have legal personality or legal capacity, one member of the group is  appointed as leader of the group. Each provision of this contract is severable and distinct from the others. If a provision is or  becomes illegal, invalid or unenforceable to any extent, it must be severed from the  remainder of the contract. This does not affect the legality, validity or enforceability of  any other provisions of the contract, which continue in full force and effect. The illegal,  invalid or unenforceable provision must be replaced by a legal, valid and enforceable  substitute provision which corresponds as closely as possible with the actual intent of the  parties under the illegal, invalid or unenforceable provision. The replacement of such a  provision must be made in accordance with Article II.11. The contract must be interpreted  as if it had contained the substitute provision as from its entry into force.  II.4.1  The contractor must comply with the minimum requirements provided for in the  tender specifications. This includes compliance with applicable obligations under  environmental, social and labour law established by Union and Community 12 