It has been mandatory for a building/property to possess an occupancy certificate and a completion certificate (CC) since 1976. Hence, a building/property that was constructed in or after 1976 must possess one. However, acquiring an OC for an old construction can prove to be a tricky business. It must ideally be in the possession of the developer, but if the developer fails to furnish one, you can always file an RTI application. Your last resort should be a series of constant follow-ups with your local municipal authority for the document.