Registration of agreement between builder and land owner ?

An agreement for sale does not create or extinguish or transfer any rights in immovable property and hence registration is not compulsory under Section 17 of IR Act.. However in manny states Ex: Maharashtra, the state Govts have made such agreements compulsorily registrable. In such states if the document is nor registered  it is not valid and is not admissible in evidence in a court of law. A subsequent buyer is not bound by such agreemnt.