Section 123C(1)(iv) in The Delhi Municipal Corporation Act, 1957
(iv)where, on an application made, in writing, by the owner or the person liable to pay the property tax, it is established that during the period the annual value is in force, such value has been reduced by reason of any substantial demolition or has suffered depreciation on account of any accident or any calamity proved to the satisfaction of the Commissioner to have been beyond the control of such owner or person, or