Sales, mortgages (other than by way of deposit of title deeds) and exchanges of immovable property are required to be registered by virtue of the Transfer of Property Act. So all the above documents have to be in writing.

Section 17 of the Act provides for optional registration. An unregistered document will not affect the property comprised in it, nor be received as evidence of any transaction affecting such property (except as evidence of a contract in a suit for specific performance or as evidence of part-performance under the Transfer of Property Act or as collateral), unless it has been registered.

Thus the doctrine of part performance dealt with under Section 53 A of the Transfer of Property Act and the provision of Section 49 of the Registration Act (which provide that an unregistered document cannot be admissible as evidence in a court of law except as secondary evidence under the Indian Evidence Act) together protect the buyer in possession of an unregistered sale deed and cannot be dispossessed. The net effect has been that a large number of property transactions have been accomplished without proper registration.

Instruments such as Agreement to Sell, General Power of Attorney and Will have been indiscriminately used to effect change of ownership. Therefore, investors in real estate have to be careful in their due diligence.