20. Exercise of powers to be subject of sanction.- Save as otherwise provided in this act, the exercise, of any power or the performance of any duty conferred or imposed upon the Council by or under this Act which will involve expenditure, shall be subject to the following conditions, namely:- (a) that such expenditure, in so far as is to be incurred in the year in which such power is exercised or duty performed, shall be provided for under a current budget-grant; and (b) that if the exercise of such powers of the performance of such duty involves or is likely to involve expenditure for any period or at any tie after the close of the said year, such expenditure shall not be incurred without the sanction of the Council. | 
