Section 23(2)(c) in The Chennai Metropolitan Water Supply and Sewerage Board's Water Tax and Sewerage Tax (Levy and Collection) Regulations, 1991
(c)If such notice is given within the last four months of the half year, the owner shall be entitled to a remission of so much not exceeding a half of the tax payable in respect of the building only for that half year as is proportionate to the number of days in that half year succeeding the demolition or destruction as the case may be.