By way of derogation from the provisions of the previous paragraph, the grant rate may be applied to the uncapped amount of actual expenditure excluding tax when unforeseeable circumstances on the part of the beneficiary due to the nature of the soil or resulting from disasters lead to a major revision of the estimate. The additional subsidy is the subject of a new order. II. – An advance may be paid on presentation of the document informing the Prefect that work on the project has begun or, in the case of authorisation for work to begin earlier, on notification of the award decision. Its amount corresponds to the local authority’s contractual commitments and may not exceed 20% of the estimated amount of the grant. III. – Payments on account, not exceeding a total of 80% of the estimated amount of the grant, taking into account the advance paid, may be paid according to the progress of the operation on the basis of supporting documents for payments made by the applicant and on production of certification of the service provided by the State department designated by the Prefect. IV. – The balance of the grant is paid after submission of supporting documents for the payments made by the applicant. These documents are accompanied by a certificate signed by the mayor, the president of the public establishment for inter-communal cooperation or the president or director of any legal entity under public law exercising competence for the construction and renovation of educational establishments attesting to the completion of the operation as well as the compliance of its characteristics with the awarding order and mentioning the final cost of the operation as well as its final financing arrangements.