You need to issue a notice to the builder to apply and handover Completion Certificate / Occupancy Certificate, within one month from the date of issue of your notice.
If the builder does not respond, file a complaint in the consumer forum, and pray the forum to issue directions to the builder to apply and obtain the above certificates.
You can also mention in the complaint that the Hon’ble Supreme Court has given a judgement in Faqir Chand Gulati vs Uppal Agencies Pvt. Ltd. & Anr on 10 July, 2008 that “Even if such a provision for providing completion certificate is not found in the agreement, the builder cannot escape the liability for securing the Completion Certificate and providing a copy thereof to the owner. The law requires the builder to obtain completion certificate of such a building.”