law: Coinage Act, 2011
  6. Coin when a legal
  
  tender.-
  1.  
  
    The
  
  coins issued under the authority of section 4 shall be a legal tender in
  
  payment or on account, in case of
  a.   a coin of any
  
  denomination not lower than one rupee, for any sum not exceeding one thousand
  
  rupees;
  b.   a half-rupee coin,
  
  for any sum not exceeding ten rupees;
  c.   any other coin, for
  
  any sum not exceeding one rupee:
  Provided that the
  
  coin has not been defaced and has not lost weight so as to be less than such
  
  weight as may be prescribed in its case.
  1.  
  
  
  2.  
  
    All
  
  new coins in the naya paisa series, designated as such under the notification
  
  of the Government of India in the Ministry of Finance, Department of Economic
  
  Affairs, Number S.R.O. 1120, dated the 11th May, 1956 issued prior to the
  
  commencement of the Indian Coinage (Amendment) Act, 1964 (17 of 1964), shall
  
  continue to be a legal tender in payment or on account, in case of,
  a.   a half-rupee or fifty
  
  naye paise coin, for any sum not exceeding ten rupees;
  b.   any other coin, for
  
  any sum not exceeding one rupee.