Contract number: [ complete ]  Contract conditions of December 2015  If no observations have been submitted or if, despite the observations submitted, the  contracting authority decides to pursue the recovery procedure, it must confirm recovery  by  formally notifying  a debit note to the contractor, specifying the date of payment. The  contractor must pay in accordance with the provisions specified in the debit note.  If the contractor does not pay by the due date, the contracting authority may, after  informing the contractor in writing, recover the amounts due:  If the contractor does not honour the obligation to pay the amount due by the date set by  the contracting authority in the debit note, the amount due bears interest at the rate  indicated in Article II.20.8. Interest on late payments will cover the period starting on the  day after the due date for payment and ending on the date when the contracting authority  receives the full amount owed.  Any partial payment is first entered against charges and interest on late payment and then  against the principal amount.  If the contract is signed by a group (joint tender), the group is jointly and severally liable  under the conditions set out in Article II.6 (liability). The contracting authority first claims  the full amount to the leader of the group. If the leader does not pay by the due date and if the amount cannot be offset in accordance  with Article II.21.2 (a), the contracting authority may claim the full amount to any other  member of the group by notifying the debit note already sent to the leader under Article  II.21.2.  Such checks and audits may be initiated at any moment during the provision of the  supplies and to five years starting from the the payment of the balance. The audit procedure is initiated on the date of receipt of the relevant letter sent by  the contracting authority. Audits are carried out on a confidential basis.  II.22.2. The contractor must keep all original documents stored on any appropriate  medium, including digitised originals if authorised under national law, for a period  of five years starting from the payment of the balance. II.22.1. The contracting authority and the European Anti-Fraud Office may check or  require an audit on the  performance of the contract . This may be carried out either  by OLAF’s own staff or by any other outside body authorised to do so on their  behalf. II.22. CHECKS AND AUDITS  II.21.4. Recovery rules in the case of joint tender  (a) by offsetting them against any amounts owed to the contractor by the European  Atomic Energy Community; (b) by calling in a financial guarantee if the contractor has submitted one to the  contracting authority; (c) by taking legal action. II.21.3 Interest on late payment  31 