I.6. PAYMENT ARRANGEMENTS  I.6.1. Pre-financing  I.6.2. Interim payment  I.6.3. Payment of the balance  1. Payments under the FWC shall be made in accordance with Article II.20, which is complemented by  Article IV.1.5 and the provisions of the specific contracts (Annexes I and IV).  2. Payments shall be executed only if the contractor has fulfilled all its contractual obligations by the  date on which the invoice is submitted. Payment requests may not be made if payments for previous  orders or specific contracts have not been executed as a result of default or negligence on the part of  the contractor.  Not applicable.  For services:  1 The contractor (or leader in case of a joint tender) shall send an invoice for monthly interim  payment, starting with the second month of provision of services and covering the services provided in  the previous month in accordance with Article II.20.6.  2 The contractor (or leader in case of a joint tender) must send any invoice for the interim payment in  paper format or via e-PRIOR.  3 All invoices shall indicate both the contractor’s and the contracting authority’s VAT number. 4. The contracting authority must approve any submitted documents or supplies/deliverables and pay  within 30 days from receipt of the invoice.  5. If the contracting authority has observations to make, it must send them to the contractor (or leader  in case of a joint tender) and suspend the time limit for payment in accordance with Article II.20.7. The  contractor (or leader in case of a joint tender) has 10 days to submit additional information or  corrections or new supplies or a new version of the document if the contracting authority requires it.  6. The contracting authority must give its approval and pay within the remainder of the time-limit  indicated in paragraph 4 above unless it rejects partially or fully the submitted documents or  supplies/deliverables.  The payment methodology will be established in the relevant specific contract.  For supplies:  For services/supplies:  1. The contractor (or leader in case of a joint tender) shall submit an invoice for payment of balance within 30 days after the end date of the specific contract in accordance with Article II.20.6.  2. The contractor (or leader in case of a joint tender) must send any invoice for the payment of balance  in paper format or via e-PRIOR.  3 All invoices shall indicate both the contractor’s and the contracting authority’s VAT number. 4. The contracting authority must approve any submitted documents or supplies/deliverables and pay  within 30 days from receipt of the invoice.  6 