Europol Public Information 3.3.3. Subcontracting - contract implementation  4. Contacts between Europol and the candidates/tenderers  4.1. Questions and answers before the time limit for receipt of tenders  4.2. Amendments to the procurement documents before the time limit for receipt of  tenders  11  Working days at Europol’s location in The Hague.  General Guidance on Europol Procurement Procedures  Page  13  of  20 Europol may, on its own initiative, modify the procurement documents by amendment if it spots  any error, inaccuracy, omission or other clerical error in the procurement documents. Clarifications / additional information will be regarded as an integral part of the procurement  documents.  Tenderers shall note that Europol is not bound to reply to questions submitted less than six (6)  working days 11  before the time limit for receipt of tenders.  Any answer/additional information provided at the request of an economic operator will be  provided simultaneously to all operators by the same means as for the procurement documents. Any request for additional information must be made in writing only. Further details about  submitting questions are specified in the Invitation.  Upon request, the contracting authority may provide additional information solely for the  purpose of clarifying the procurement documents.  Contacts between Europol and candidates or tenderers are prohibited throughout the procedure  save in exceptional circumstances and under the following conditions only:  Europol recognises that arrangements in relation to sub-contracting may (within limits) be subject  to future change. If the subcontracting arrangement has changed this must be notified to Europol  in a signed letter.  During the execution of the contract, the contractor will need Europol’s express authorisation to  replace a subcontractor with another subcontractor and/or to subcontract tasks for which  subcontracting was not envisaged in the original tender, in compliance with the provisions on  subcontracting foreseen in the contract.  • under no circumstances can the main contractor avoid liability towards Europol on the  grounds that the subcontractor is at fault.  • Europol does not acknowledge any contractual link between itself and subcontractor(s)  and will treat all contractual matters (e.g. payment) exclusively with the main contractor,  whether or not the tasks are performed by a subcontractor;  Once the contract has entered into force, the successful tenderer shall retain full liability towards  Europol for the performance of the contract as a whole. Europol will not have any direct legal  commitment with the subcontractor(s). Accordingly: 