261.5.14. For the purpose of determining the totals of the entered or adjusted values to be averaged, the property assessment roll is used, taking into account not only any alteration made to that roll before 1 January or 31 December of the current fiscal year but also any alteration retroactive to the relevant date or any earlier date that is made, even after the end of the fiscal year, in time for the supplement that must be paid or the overpayment that must be refunded as a result of the alteration to have an effect on the revenues recorded in the financial report produced for the fiscal year.