Hello Raju, Certificate of Occupancy or completion certificate is a document which is issued at the end of the construction by a local government agency or planning authority. The document is a proof of the building's compliance with applicable building codes and other laws. A flat owner can occupy an apartment only once the OC is issued, as per law. The OC also plays a significant role while applying for home loan or loan to purchase a resale flat.
Yes, I am agreed with Apurva. If there is no OC, the Palike can also initiate action against the flat owners, as the law says no person can move into a building without the OC. There is also a chance that the electricity and water connection could be cut if the owner does not have the OC. If your building does not have an OC, a flat owner or buyer can approach their local body directly.