The Builder is not agreeing to register because it is not part of individual owners parking area and he is not supposed to sell it separately. .You please find out from the plan how that particular area is marked in the Plan /Layout.
Supreme court has observed in ", Nahalchand Laloochand Pvt. Ltd. v. Panchali Co-operative Housing Society Ltd", “The promoter has no right to sell any portion of such building which is not ‘flat’ within the meaning of Section 2(a-1) and the entire land and building has to be conveyed to the organisation; the only right remains with the promoter is to sell unsold flats. It is, thus, clear that the promoter has no right to sell ‘stilt parking spaces’ as these are neither ‘flat’ nor appurtenant or attachment to a ‘flat’.the Hon’ble Supreme Court rejected the argument of a real estate development company that they are entitled to sell garages or stilt parking areas as separate flats to owners who intend to use it as parking facilities."The promoter has no right to sell any portion of such building which is not flat within the meaning of Section 2(a-1) and the entire land and building has to be conveyed to the organisation. The only right remains with the promoter is to sell unsold flats.
The court ruled that builders or promoters cannot sell parking areas as independent units or flats as these areas are to be extended as “common areas and facilities” for the owners. Also, the Court said that the developer is only entitled to charge price for the common areas and facilities from each flat purchaser in proportion to the carpet area of the flat.
You should insist the builder for the registration of it as you are purchasing it as an individual flat owner, since the society has not formed now it is not part of the society .actually this should have formed part of your sale agreement.Since the sale of car parking slots is illegal, its purchase also becomes null and void. After a housing society has been registered and taken charge, it becomes the owner of all parking spaces within the project.