law: Registration Act, 1908
  18. Documents of which registration is optional
  Any of the following documents may be registered under this Act,
  
  namely:-
  (a) instruments (other than instruments of gift and wills) which
  
  purport or operate to create, declare, assign, limit or extinguish, whether in
  
  present or in future, any right, title or interest, whether vested or
  
  contingent, of a value less than one hundred rupees, to or in immovable
  
  property;
  (b) instruments acknowledging the receipt or payment of any
  
  consideration on account of the creation, declaration, assignment, limitation
  
  or extinction of any such right, title or interest;
  (c) leases of immovable property for any term not exceeding one
  
  year, and leases exempted under section 17;
  16[(cc) instruments transferring or assigning any decree or
  
  order of a court or any award when such decree or order or award purports or
  
  operates to create, declare, assign, limit or extinguish, whether in present or
  
  in future, any right, title or interest, whether vested or contingent, of a
  
  value less than one hundred rupees, to or in immovable property;]
  (d) instruments (other than wills) which purport or operate to
  
  create, declare, assign, limit or extinguish any right, title or interest to or
  
  in movable property;
  (e) wills; and
  (f) all other documents not required by section 17 to be
  
  registered.