(i) Advances shall be considered as an increase in the illiquid balance from the date of the advance. (ii) refunds due to the contractor`s control shall be considered as a reduction in the cash balance from the date on which the cheque was received by the governmental authority designated by the contract agent. (iii) Liquidations by deduction of payments to the contractor shall be considered as a reduction in the illiquid balance from the date on which the holder provides the holder with complete and accurate data for the preparation of each voucher. The credits resulting from these deductions shall be made after the approval of the supporting documents by the paying agent, on the basis of the certification of the dates in force by the contractor. . . .