(3)If the assessing authority is of opinion that any person has completed the construction of a building having a floorage of one thousand square feet or more after the 2nd day of March, 1961, then, notwithstanding anything contained in sub-section (1), it may serve a notice upon the owner of such building requiring him to furnish within such period, not being, less than thirty days as may be specied in the notice, a return in the prescribed form and verified in the prescribed manner and containing such particulars in respect of the building as may be required in the notice.
