law: Expenditure-Tax Act, 1987 
  11. Chargeable expenditure escaping assessment
  
   
  If- 
  (a) the 16[Assessing] Officer has
  
  reason to believe that by reason of omission or failure on the part of the assessee
  
  to make a return under section 8 for any assessment year or to disclose wholly
  
  and truly all material facts necessary for his assessment for any assessment
  
  year, chargeable expenditure for that year has escaped assessment or has been
  
  under-assessed, or
  (b) notwithstanding that there has been no
  
  omission or failure as mentioned in clause (a) on the part of the assessee, the
  
  16[Assessing] Officer has, in consequence of information in his
  
  possession, reason to believe that chargeable expenditure assessable in any
  
  assessment year has escaped assessment or has been under assessed, he may, in
  
  cases falling under clause (a), at any time, and in cases failing under clause
  
  (b), at any time within four years from the end of that assessment year, serve
  
  on the assessee a notice containing all or any of the requirements which may be
  
  included in a notice under section 8 and may proceed to assess or reassess the
  
  chargeable expenditure, and the provisions of this Act shall, so far as may be,
  
  apply, as if the notice were a notice issued under that section.