On registering each participant obtains a Participant Identification Code (PIC, 9-digit number)  which acts as its unique identifier in the Participant Register. A participant needs to register  only once – the information provided can be further updated or re-used by the participant in  other European Commission's calls for tenders. Economic operators can submit a tender either as a sole tenderer or as a group of tenderers.  In either case subcontracting is permitted. In order to fulfil the selection criteria set out in  Section 3.2  the tenderer can rely on the  capacities of subcontractors or other entities (not subcontractors).  The role of each entity involved in a tender (hereafter referred to as  involved entity ) must be  clearly specified: sole tenderer, member of a group or Group leader, subcontractor or an  entity on whose capacities the tenderer relies to fulfil the selection criteria 3 . This applies also  where the  involved entities  belong to the same economic group.  2.4. Ways to submit a tender: how can economic operators organise  themselves to submit a tender?  2.4.1. Joint tenders  11 3  Such an entity is not considered a subcontractor, see Section 2.4.3.  4  References to  tenderer  or  tenderers  in this document shall be understood as covering both sole tenderers and  groups of economic operators submitting a joint tender. A joint tender is a situation where a tender is submitted by a group (with or without legal  form) of economic operators regardless of the link they have between them. The group as a  whole is considered a tenderer 4 . All members of the group assume joint and several liability towards the  Contracting authority for the performance of the contract as a whole. Group members must appoint a  Group leader  and a single point of contact authorised to  act on their behalf in connection with the submission of the tender and all relevant  questions, clarification requests, notifications, etc., that may be received during the  evaluation, award and until the contact signature. The model power of attorney attached in  Annex 3  is to be used . The joint tender must clearly indicate the role and tasks of each member and of the  Group  leader  who will act as the  Contracting authority 's contact point for the contract's  administrative or financial aspects and operational management. The  Group leader  will have  full authority to bind the group and each of its members during contract execution. If the joint  tender is successful, the  Contracting authority  shall sign the contract with the Group leader,  authorized by the other members to sign the contract on their behalf via power of attorney  drawn up in the model attached in  Annex 3 .  Changes in the composition of the group during the procurement procedure (after the  submission deadline and before contract signature) shall lead to rejection of the tender except  in case of: 