Section 109(4) in The Chandernagore Municipal Corporation Act, 1990
(4)A new valuation list under sub-sections (1) and (3) shall, unless otherwise directed by the State Government, be prepared in the same manner once in every six years:Provided that if an existing valuation list is not revised for any unavoidable reason, the validity of operation of such valuation list shall not be called in question until a new valuation list takes effect under this Act.