Title Deed from Builder.

Q: Title Deeds of LandI purchased a flat from a private builder. There are 17 flats (including pent house). We 17 flat owners formed an association (Society) for maintenance and upkeepment. The society is not yet registered. The Builder has not so far surrendered Main Title deed of the plot on which the Apartment was built. All the flats have been duly registered with Registrar of concerned Panchayat. Now, kindly guide us whether Master Title Deed is necessary to preserve at the Society to prevent any fraudulent transaction by the owner ? If so, what steps should we take.