law: Expenditure-Tax Act, 1987 
  20. Notice of demand 
  When any tax, interest, penalty or any other
  
  sum is payable under this Act, the 16[Assessing] Officer shall serve
  
  upon the assessee a notice of demand in the prescribed form26,
  
  specifying the sum so payable and the amount of chargeable expenditure in
  
  relation to which such sum is payable.