II.20.8. Interest on late payment  II.21.1. Principle  II.21.2.  Recovery procedure II.21.3.  Interest on late payment II.21.4.  Recovery rules in case of a joint tender On expiry of the payment periods specified in Article I.6, the contractor (or leader in case of a joint tender) is  entitled to interest on late payment at the rate applied by the European Central Bank for its main refinancing  operations in euros (the reference rate) plus eight points. The reference rate is the rate in force, as published  in the C series of the Official Journal of the European Union, on the first day of the month in which the  payment period ends.  Suspension of the payment period as provided for in Article II.20.7 is not considered as giving rise to late  payment. Interest on late payment covers the period running from the day following the due date for payment up to and  including the date of payment as defined in Article II.20.1.  However, when the calculated interest is EUR 200 or less, it must be paid to the contractor (or leader in case  of a joint tender) only if it requests it within two months of receiving late payment. II.21. RECOVERY  If an amount is to be recovered under the terms of the FWC, the contractor must repay the contracting  authority the amount in question.  Before recovery, the contracting authority must formally notify the contractor of its intention to recover the  amount it claims, specifying the amount due and the reasons for recovery and inviting the contractor to make  any observations within 30 days of receipt.  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:  (a) by offsetting them against any amounts owed to the contractor by the contracting authority or the  European Union;  (b) by calling in a financial guarantee if the contractor has submitted one to the contracting authority;  (c) by taking legal action.  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 of two or more economic operators (joint tender), all members of the  group are jointly and severally liable under the conditions set out in Article II.6. The contracting authority first  claims the full amount to the leader of the group.  33 