Hi. Yes you can form and register a co-operative housing society if 51% flat bookings are done by the builder . The society formation will not hamper the construction work. You can request your builder to form and register a housing society of the flat allottees. Such a society has to be formed within 3 months of 51% bookings made by the builder. If the builder does not form a society then the allottees can apply to RERA which will pass necessary order to enable the allottees to form and register a housing society.