law: Expenditure-Tax Act, 1987 
  9. Assessment 
  (1) For the purpose of making an assessment
  
  under this Act, the 16[Assessing] Officer may serve on any person
  
  who has furnished a return under section 8 or upon whom a notice has been served
  
  under sub-section (2) of section 8 (whether a return has been furnished or not)
  
  a notice requiring him on a date therein to be specified, to produce or cause
  
  to be produced such accounts or documents or other evidence as the 16[Assessing]
  
  Officer may require for the purposes of this Act and may, from time to. time,
  
  serve further notices requiring the production of such further accounts or
  
  documents or other evidence as he may require.
  (2) The 16[Assessing] Officer,
  
  after considering such accounts, documents or other evidence, if any, as he has
  
  obtained under sub-section (1) and after taking into account any relevant
  
  material which he has gathered, shall, by an order in writing, assess the
  
  chargeable expenditure and the amount of tax payable on the basis of such
  
  assessment.