As an exception to the previous paragraph, the subsidy rate may be applied to the uncapped amount of actual expenditure excluding tax when unforeseeable circumstances for the beneficiary due to a change in regulations lead to a significant change in the forecast cost. The additional subsidy will be the subject of a new order. II. – An advance representing 20% of the estimated amount of the grant is paid on presentation of the document informing the Prefect of the département that work on the project has begun, or in the case of an earlier start, when the grant awarding order is notified. III. – Payments on account, not exceeding a total of 80% of the estimated amount of the grant, may be made depending on the progress of the operation, on the basis of supporting documents for payments made by the departmental and territorial fire and rescue services or by the Marseille municipality. IV. – The balance of the subsidy is paid after transmission of the supporting documents for the payments made by the public institution, which must be accompanied by a certificate signed by the Chairman of the Board of Directors or by the Mayor of Marseille attesting to the completion of the operation and the compliance of its characteristics with the allocation order and stating the final cost of the operation as well as its final financing terms.