law: Negotiable Instruments Act, 1881 
  79. Interest when rate specified 
  When interest at a specified rate is expressly made payable on a
  
  promissory note or bill of exchange, interest shall be calculated at the rate
  
  specified, on the amount of the principal money due thereon, from the date of
  
  the instrument, until tender or realization of such amount, or until such date
  
  after the institution of a suit to recover such amount as the court directs.