submitted with the interim progress reports; and  (b) the amounts claimed as incidental expenditure have actually and necessarily been incurred by  the Consultant in accordance with the requirements of the terms of reference of the contract.  (c) On the basis of his/her verification, the auditor submits to the Consultant an expenditure  verification report in accordance with the model in Annex VII. .  28.4. The Consultant grants the auditor all access rights mentioned in Article 25.  28.5. The Contracting Authority reserves the right to require that the auditor be replaced if considerations  which were unknown when the Contract was signed cast doubt on the auditor's independence or  professional standards.  29.1. Payments will be made in accordance with one of the two options below, as identified in Article 3 of  the Special Conditions.  1. A pre-financing payment, if requested by the Consultant, of an amount as requested up to the  maximum specified below, within 45 days of receipt by the Contracting Authority of the Contract  signed by both parties, of a request for payment and of a financial guarantee, as defined in  Article 30. The pre-financing shall be of a maximum of 30 % of the total contract amount if the  implementation period of the tasks is 24 months or less, and 20 % of the total contract amount if the implementation period of the tasks is more than 24 months.  4. The balance of the final value of the contract after verification, subject to the maximum contract  value stated in Article 3 of the Special Conditions, after deduction of the amounts already paid,  within 45 days of the Contracting Authority receiving an invoice accompanied by the final  progress report and a final expenditure verification report subject to approval of those reports in  accordance with Article 27.  3. The invoices must be paid such that the sum of payments does not exceed 90% of the maximum  contract value stated in Article 3 of the Special Conditions; the 10% being the minimum final  payment.  1. a pre-financing payment up to 30 % of the contract value stated in Article 3 of the Special  Conditions within 45 days of receipt by the Contracting Authority of the Contract signed by both  parties, and of a financial guarantee, as defined in Article 30;  2. the balance of the contract value stated in Article 3 of the Special Conditions within 45 days of the Contracting Authority receiving a final invoice accompanied by the final progress report,  subject to approval of that report in accordance with Article 27  29.2. The payment deadline of 45 calendar days referred to in Article 29.1 shall expire on the date on which  the Contracting Authority’s account is debited. Without prejudice to Article 36.3, the Contracting  Authority may halt the countdown towards this deadline for any part of the invoiced amount disputed  by the Project Manager by notifying the Consultant that part of the invoice is inadmissible, either  because the amount in question is not due or because the relevant report cannot be approved and  the Contracting Authority thinks it necessary to conduct further checks. In such cases, the Contracting  Authority must not unreasonably withhold any undisputed part of the invoiced amount but may request  clarification, alteration or additional information, which must be produced within 30 days of the request.  The countdown towards the deadline will resume on the date on which a correctly formulated invoice  2. Six-monthly interim payments, if any, as indicated in Article 7.2 of the Special Conditions, within  45 days of the Contracting Authority approving an interim progress report and an expenditure  verification report accompanied by an invoice, in accordance with Article 27. Such interim  payments shall be of an amount equivalent to the costs incurred on the basis of the expenditure  verification reports. When 80% of the contract amount has been paid (pre-financing and interim  payments) the amounts due to the Consultant shall be deducted from the pre-financing payment  until it is completely reimbursed before any additional payments will be made.  Page 13 of 19  The Contracting Authority will make payments to the Consultant in the following manner:  Option 2: Global price contract  Option 1: Fee-based contract  ARTICLE 29. PAYMENT AND INTEREST ON LATE PAYMENT  The Contracting Authority will make payments to the Consultant in the following manner: 